Toyota Sienna Forum - siennachat.com banner
1 - 18 of 18 Posts

·
Registered
21 Sienna LE Cypress Green
Joined
·
27 Posts
Discussion Starter · #1 ·
I don't know much about this particular fuel other than apparently they say it's fine to use in modern vehicles...so wondering if anyone has been using, and has anything to report. Thanks! ( I have a 21 LE FWD).
 

·
Registered
2021 Sienna XLE
Joined
·
663 Posts
Unleaded 88 is usually 15% ethanol compared to normal unleaded which is typically 10% ethanol. Toyota says up to 15% ethanol is acceptable. Note that ethanol has less energy per gallon, so fuel mileage will be slightly lower.
 

·
Registered
Joined
·
763 Posts
don't use it. its 15% ethanol fuel, and the sienna doesn't like the higher ethanol content, its MPGs drop around 10%.
You'd think that zero ethanol, like they sell at a couple of places in the area, would give you better mpg - but somehow it doesn't (established experimentally)
 

·
Registered
2021 Sienna XLE
Joined
·
663 Posts
You'd think that zero ethanol, like they sell at a couple of places in the area, would give you better mpg - but somehow it doesn't (established experimentally)
The regular fuel containing ethanol is stated as "up to 10%" ethanol, so the ethanol amount can vary based on availability. With high mileage vehicles like the Sienna, it is hard to notice a difference. Try driving a big motorhome getting 7 mpg. With 10% ethanol, the mileage is closer to 6 mpg.
 

·
Registered
Joined
·
763 Posts
The regular fuel containing ethanol is stated as "up to 10%" ethanol, so the ethanol amount can vary based on availability. With high mileage vehicles like the Sienna, it is hard to notice a difference. Try driving a big motorhome getting 7 mpg. With 10% ethanol, the mileage is closer to 6 mpg.
If 0% ethanol gas yields 15% better mpg in the case of a motorhome, why wouldn't it produce a similar increase of mpgs' in a more fuel-efficient vehicle? I mean, what's the mechanism of it? That the Toyota hybrid engines are less affected by lower energy density?
 

·
Registered
Joined
·
4 Posts
Not quite apples to apples but I did a trip to Cedar Break, UT climbing to 10,000 ft on regular 87 w/ 10% ethanol and averaged 31mpg. The following trip, did another trip to Denver, CO climbing up to 12,000 ft on 88 w/ 0% ethanol and averaged 33mpg. I can't remember the price spread between 87 and regular 88 but with my one data point, as long as the price difference is less than 6%, you'll make out ahead with ethanol free 0% gas. Subjectively, the engine felt like it had more oomph climbing and seemed to be a little less coarse sounding.

These values are all hand calculated. The computer on mine is about 9% optimistic, so the dash will read 36mpg but it works out to around 33mpg. This is after reseting both the Trip A and fuel economy readout after each fill. All the other cars I've had (mostly VW) all achieve or beat their combined mpg but the two Toyotas I've had had fallen below. Wish the Sienna got the 36mpg it's rated for but 33mpg is still best in class. 33mpg is my tracked average over 35k miles with mostly highway driving of speeds above 70mph.

The Sienna can take up to 15% ethanol. I'm currently trying 1 tank of 91 octane but suspect there will be minimal improvement, and by the numbers not worth the price difference. The Sienna has a high compression ratio (14.x:1) and is rated for minimum 95 RON in the UK with their Highlander Hybrid (direct carryover to the US) which converts to around 92 AKI in the US. The Sienna stateside says 87 AKI or higher hence why I'm trying a tank of 91. So far, with just around 60 miles on the tank, no improvement with mpg but subjectively the engine does seem to sound quieter and more refined. For reference, this is in Phoenix, AZ with temps well above 100F and mixed driving so far.
 

·
Registered
2021 Sienna XLE
Joined
·
663 Posts
The regular fuel containing ethanol is stated as "up to 10%" ethanol, so the ethanol amount can vary based on availability. With high mileage vehicles like the Sienna, it is hard to notice a difference. Try driving a big motorhome getting 7 mpg. With 10% ethanol, the mileage is closer to 6 mpg.
It may be because the motorhome was basically all highway miles all requiring lots of power to overcome the weight and air resistance. With a car, the engine will run more at a very light load, where the difference in energy content is less pronounced. Just a theory though.
 

·
Registered
2014 Sienna LE
Joined
·
194 Posts
At 116 kBtu/gal for pure gasoline (this value could vary a bit) and 77 kBtu/gal for ethanol, then E10 has an energy content of 112 kBtu/gal and E15 110 kBtu/gal. That's a difference of less than 2%. So if you normally get 35 MPG eith E10, you'd get 34.4 MPG with E15. In theory, there's a LOT of various factors here that mean in practice it's not so cut and dried. These include the energy content of the base gasoline, which varies, how the engine does or does not compensate for the difference in energy content, etc.

If you want to do the math based on energy content to see what's a better value, assuming the MPG varies linearly with energy content, I did a previous post on how to do that math:
Around here you can get E10 or E15, with one gas station chain selling both. Well, both are up to 10 or up to 15%, not guaranteed to have that much. I don't have the math I did handy to prove this, but assuming they are actually 10 and 15% ethanol, at $3.849/gal for E10 and $3.649 for E15, the E15 worked out to just slightly cheaper per unit of energy than the E10. Something like 3.4 cents/Btu for the E10 and 3.3 cents/Btu for the E15 if I remember right. This calculation was done with the assumption of 116 kBtu/gal for gasoline and 77 kBtu/gal for ethanol, based on Google searches.

Actually we can redo that math, it's fairly easy. For E10, you've got 116*0.9 + 77*0.1 = 112.1 kBtu/gal. $3.849/112.1 = $0.0343/kBtu. For E15, you've got 116*.85 + 77*0.15 = 110.2 kBtu/gal. $3.649/110.2 = $0.0331/kBtu. So the E15 here would be about 96.5% the cost for the same amount of total available energy. Substitute your own E10/E15 $/gal prices into these equations to determine if it is cheaper or more expensive where you live. I've definitely done this calculation before and had it work out that the more expensive E10 was cheaper, just depends on the price spread.

Summary: Depending on the price difference between E10 and E15 it may ultimately be slightly cheaper, despite a reduction in MPG with the higher ethanol gas, but you need to do some math to figure out for sure based on the local price spread between E10 and E15. Caveat: If your "up to 10%" gas is actually 5% ethanol, while the "up to 15%" gas is actually 15% ethanol, this completely changes the equation. But you can't know the actual % of ethanol in the gas, which may vary from time to time, so you can only do the math with the assumption the actual content is the "up to" content.

You can, of course, do the same calculation to figure out if ethanol free gas (if available in your area) is a better deal than E10 or E15, price wise.

If, and only if, you have a flex fuel vehicle rated for E85, and I don't believe any Siennas can run E85 anyway, but since it was mentioned, you can also do the same calculation for E85 vs E10 or E15. For E85 to calculate the energy content of a gallon of gasohol, it would be 116*0.15 + 77*0.85 = 82.85 kBu/gal. I don't know what E85 costs around here, but we can instead set up an equation to solve for the price E85 would need to be per gallon to equal the energy content of E10 or E15. Since we know E10 was $0.0343/kBtu, our equation would be 0.0343 ($/kBtu) = x ($/gal)*(1/82.85) (gal/kBtu). Solving for x, we get $2.845/gal. So if E10 costs $3.849/gal, E85 would need to be less than $2.845/gal for it to make financial sense to use over E10 (and your vehicle has to be flex fuel capable). My gut feeling is I've never seen a price spread on E10 vs E85 that would make E85 economically advantageous to use over E10, even if I owned a vehicle that could run it, which I don't. My personal preference would be no ethanol at all, due to the well known downsides of ethanol in gas, plus the subsidies that make ethanol as cheap as it is in the US...but we won't continue down that path here. Finally, on the last practical note, you'd also have to factor in the amount of extra time it would take you and if that's worth it to you, since you'd only get 74% the MPG running E85 vs E10, so you'd have to fill up a lot more often.
You'd think that zero ethanol, like they sell at a couple of places in the area, would give you better mpg - but somehow it doesn't (established experimentally)
Yup, same. I've tried E0 and not seen an increase in MPG on my 2014 Sienna. My brother, who has tracked MPG for over a year on every fill-up of his motorcycle, which is his primary commuting vehicle, also has not seen a difference between E10 and ethanol free.

The regular fuel containing ethanol is stated as "up to 10%" ethanol, so the ethanol amount can vary based on availability. With high mileage vehicles like the Sienna, it is hard to notice a difference. Try driving a big motorhome getting 7 mpg. With 10% ethanol, the mileage is closer to 6 mpg.
Yup, and E15 is "up to" 15% ethanol. Just like E10, you aren't guaranteed a specific ethanol content. However, you can probably be assured of at least 5% ethanol, because I'm 99% sure the reason E15 is sold as 88 octane is because if you take 87 octane gas (of any ethanol content) and mix in 5% ethanol, you get 88 octane gas. I did the math on this. So the ethanol content of E15 is likely whatever the ethanol content of the E10 gas a particular station sells plus 5% ethanol.

Also, in theory, you should see a bigger difference in MPG on higher MPG vehicles, not lower ones. Because 2% of 35 MPG is 0.7 MPG, but 2% of 7 MPG is 0.14 MPG.
 

·
Registered
Joined
·
763 Posts
At 116 kBtu/gal for pure gasoline (this value could vary a bit) and 77 kBtu/gal for ethanol, then E10 has an energy content of 112 kBtu/gal and E15 110 kBtu/gal. That's a difference of less than 2%. So if you normally get 35 MPG eith E10, you'd get 34.4 MPG with E15. In theory, there's a LOT of various factors here that mean in practice it's not so cut and dried. These include the energy content of the base gasoline, which varies, how the engine does or does not compensate for the difference in energy content, etc.

If you want to do the math based on energy content to see what's a better value, assuming the MPG varies linearly with energy content, I did a previous post on how to do that math:
Oh, I don't know if I would dare to use the "linear", or proportional approach you mentioned above. I would guess the energy content of ethanol vs. "gasoline" would be measured in the lab conditions by oxidizing them 100% into H2O and CO2 in a calorimeter of some nature, whereas an ICE is likely unable to reproduce this feat - at least not across the whole range of operational conditions. Also, the combustion process is a lot more intricate process than just combining every C and H stoichiometrically with oxygen in one stage, so there would surely be synergies or antergies involved.

Empirically, I believe that what we see is "inconclusive" for E0 vs. E10; some people find a measurable difference, others don't.
 
  • Like
Reactions: jseyfert3

·
Registered
Joined
·
208 Posts
Responding to original post. Yes i have tried 88 oct (15% ethanol). I have no problems with it so far. I switch regularly between 87oct (E10) and 88oct. The Sienna's ECU should be able to detect and adjust accordingly. I have no concerns about using either because I have used Ethanol fuels extensively in my other non-Toyota vehicles.

I have owned several Subaru's (WRX and STI's) - they are turbocharged high performance cars. We have modified them to use e85 (up to 85% ethanol). We do this because its cheaper and ethanol has great anti-knock properties. It is less susceptible to knock because it burns cooler and high 105+ octane rating. With turbo cars it is very important to keep things cool under the hood. Otherwise, knocking (ping) will cause your timing to be retarded and you loose power (and higher fuel consumption). Please note E85 states that the ethanol content might change between 50-85% ethanol because of winter formulation etc. So we do have be aware that our cars might run rich sometimes (which affects air/fuel ratios).

Anyway - going back to Sienna's. Dont worry about E15 vs E10. Our engines have been tested extensively by Toyota to take both fuels and adjust accordingly. That 5% additional ethanol is nothing. The US has been producing/using Ethanol for decades.
 

·
Registered
21 Sienna LE Cypress Green
Joined
·
27 Posts
Discussion Starter · #12 ·
Responding to original post. Yes i have tried 88 oct (15% ethanol). I have no problems with it so far. I switch regularly between 87oct (E10) and 88oct. The Sienna's ECU should be able to detect and adjust accordingly. I have no concerns about using either because I have used Ethanol fuels extensively in my other non-Toyota vehicles.

I have owned several Subaru's (WRX and STI's) - they are turbocharged high performance cars. We have modified them to use e85 (up to 85% ethanol). We do this because its cheaper and ethanol has great anti-knock properties. It is less susceptible to knock because it burns cooler and high 105+ octane rating. With turbo cars it is very important to keep things cool under the hood. Otherwise, knocking (ping) will cause your timing to be retarded and you loose power (and higher fuel consumption). Please note E85 states that the ethanol content might change between 50-85% ethanol because of winter formulation etc. So we do have be aware that our cars might run rich sometimes (which affects air/fuel ratios).

Anyway - going back to Sienna's. Dont worry about E15 vs E10. Our engines have been tested extensively by Toyota to take both fuels and adjust accordingly. That 5% additional ethanol is nothing. The US has been producing/using Ethanol for decades.
Super helpful, appreciate your insights.
 

·
Registered
Joined
·
91 Posts
A new station just got built by my work and they have that new E15 88 octane for 10 cents per gallon cheaper than E10 87 regular unleaded. Haven't tried it yet in the Sienna, but my 2012 Volvo XC60 got about 3 tank of it and fuel economy fell from a consistent 20.5-21.2 on the 93 it's supposed to have to 19.2. Fuel range dropped from 350 miles per tank to just barely over 300. Now that prices are falling back down to at least slightly less irrational numbers, I'm getting 350+ miles per tank on 93 again.

Ethanol is not as energy dense as gasoline, but it's octane rating is much higher. The Volvo didn't even have that much detonation running E15 88, where it detonates violently in protest of 87 octane. My company work van, a 2020 GMC Savana is perfectly happy with the E15 88. It gets 15 MPG no matter what, so the overall effect is lower. I'd imagine that in the Sienna, it would lower your MPGs more substantially, because of it's excellent baseline fuel economy. When you get 40 MPG, a 5% drops has a much greater affect vs losing 5% of 15 MPG.
 

·
Registered
Joined
·
763 Posts
A new station just got built by my work and they have that new E15 88 octane for 10 cents per gallon cheaper than E10 87 regular unleaded. Haven't tried it yet in the Sienna, but my 2012 Volvo XC60 got about 3 tank of it and fuel economy fell from a consistent 20.5-21.2 on the 93 it's supposed to have to 19.2. Fuel range dropped from 350 miles per tank to just barely over 300. Now that prices are falling back down to at least slightly less irrational numbers, I'm getting 350+ miles per tank on 93 again.

Ethanol is not as energy dense as gasoline, but it's octane rating is much higher. The Volvo didn't even have that much detonation running E15 88, where it detonates violently in protest of 87 octane. My company work van, a 2020 GMC Savana is perfectly happy with the E15 88. It gets 15 MPG no matter what, so the overall effect is lower. I'd imagine that in the Sienna, it would lower your MPGs more substantially, because of it's excellent baseline fuel economy. When you get 40 MPG, a 5% drops has a much greater affect vs losing 5% of 15 MPG.
These facts and figures have corroborated that I have come to think about the gasoline grades with high[er than usual] alcohol content.... for some vehicles the difference would be very visible - much larger than could be explained by merely the energy density difference beween the E15 and the E10. For other vehicles there will be little or no difference. Which reminds us that in real life things are rarely linear or straightforward :)
 

·
Registered
Joined
·
208 Posts
A new station just got built by my work and they have that new E15 88 octane for 10 cents per gallon cheaper than E10 87 regular unleaded. Haven't tried it yet in the Sienna, but my 2012 Volvo XC60 got about 3 tank of it and fuel economy fell from a consistent 20.5-21.2 on the 93 it's supposed to have to 19.2. Fuel range dropped from 350 miles per tank to just barely over 300. Now that prices are falling back down to at least slightly less irrational numbers, I'm getting 350+ miles per tank on 93 again.

Ethanol is not as energy dense as gasoline, but it's octane rating is much higher. The Volvo didn't even have that much detonation running E15 88, where it detonates violently in protest of 87 octane. My company work van, a 2020 GMC Savana is perfectly happy with the E15 88. It gets 15 MPG no matter what, so the overall effect is lower. I'd imagine that in the Sienna, it would lower your MPGs more substantially, because of it's excellent baseline fuel economy. When you get 40 MPG, a 5% drops has a much greater affect vs losing 5% of 15 MPG.
Your test in the Volvo between Premium gas and 88oct (e15) will yield similar results if you put 87oct (e10) regular Gas. If your car recommends Premium gas - do not put e15 88oct. If you put e15 your engine o2 sensor will think it is not getting enough gasoline hence will command the ecu to inject more of e15 fuel.

What I did to my 2004 WRX and 2005 STi involves remapping the ECU (reflash) and changing injectors so that it will compensate for the conversion from 93oct premium to 85% (e85)ethanol. Basically, we add around 15% more fuel (e85). Please do not confuse this as e15 (88 oct).
 

·
Registered
Joined
·
91 Posts
Your test in the Volvo between Premium gas and 88oct (e15) will yield similar results if you put 87oct (e10) regular Gas. If your car recommends Premium gas - do not put e15 88oct. If you put e15 your engine o2 sensor will think it is not getting enough gasoline hence will command the ecu to inject more of e15 fuel.

What I did to my 2004 WRX and 2005 STi involves remapping the ECU (reflash) and changing injectors so that it will compensate for the conversion from 93oct premium to 85% (e85)ethanol. Basically, we add around 15% more fuel (e85). Please do not confuse this as e15 (88 oct).
The only difference in how the Volvo runs between 87 and 93 is the fact that there is detonation and it's not as fast on 87. There is no difference in fuel economy at 10% ethanol.
 

·
Registered
Joined
·
208 Posts
The only difference in how the Volvo runs between 87 and 93 is the fact that there is detonation and it's not as fast on 87. There is no difference in fuel economy at 10% ethanol.
Do you have a 3.2 N/A V6 or 3.0 T6 turbo engine ? Turbo's are more prone to pinging so i doubt you will even consider putting 87oct in that. Let me know also if Volvo "recommends" or specifically mention what type of gas is needed.
 

·
Registered
Joined
·
91 Posts
Do you have a 3.2 N/A V6 or 3.0 T6 turbo engine ? Turbo's are more prone to pinging so i doubt you will even consider putting 87oct in that. Let me know also if Volvo "recommends" or specifically mention what type of gas is needed.
I have the 3.0 T6. Over the course of 225,000 miles, I've experimented with every single type, brand, and octane of gasoline available. I drive for Uber and Lyft so any savings in fuel are greatly appreciated, hence the 2022 Sienna. Per Volvo's manual, "91 octane is recommended for best performance, but 87 won't harm engine reliability."
 
1 - 18 of 18 Posts
Top