This is mostly intended for those towing with a 2nd generation Toyota Sienna (2007 thru 2010) with or without a tow prep package, but anyone else who wants to weigh-in is welcome to.
I have a 2008 Sienna Limited AWD that I bought without the tow prep package since I had no intention of towing. Then last year we bought our R-POD travel trailer. The 2008 Sienna sales brochure as well as the local dealer told me that the tow prep package consisted of a heavy-duty (HD) radiator, HD fan, 150-amp alternator, and a power steering cooler. Further discussions with the parts and service folks at the dealer determined that all 2008 Siennas came with these items â€“ whether or not they had the â€śtow prep packageâ€ť. This package was a $220 factory option, and no one could tell me why Toyota was charging $220 for items that were standard on the vehicle. The service manager said he thought I would be good-to-go if I added an auxiliary transmission oil cooler, which I did.
It never set right with me that my Sienna was officially rated (according to a VIN lookup) to tow only 1200 pounds, but apparently had everything it needed to tow 3500 pounds. So about 6 months ago, I e-mailed Toyota corporate (numerous times) asking about this discrepancy. They kept sending me replies apologizing for the delay in getting me an answer, and I had to keep e-mailing them over and over. Finally yesterday I get an answer from Toyota corporate. Yes, the four items previously identified as being part of the tow prep package were standard on all 2008 Siennas. And the e-mail said the tow prep package consisted of only an engine oil cooler.
I called a local Toyota dealership, and the parts person thought that all 2008 Siennas came with an engine oil cooler, so he speculated that the one in the tow prep package must be heavier duty. The parts person also said that he could find two engine oil coolers for my vehicle, and one of the two was described as being for the 3500 pound towing prep package. However, both of the engine oil coolers had the same Toyota part number. He is going to contact his district manager for help in sorting this out.
I have also found comments on forums saying that you probably donâ€™t need the engine oil cooler if you donâ€™t tow at high speeds on level highways or tow up hills with the metal â€“to-the-petal. (The theory being that the engine would only produce excessive oil temps if you were at 80% or more of the rated HP.)
Other posts speculated that one could run with a full synthetic engine oil in lieu of an engine oil cooler since engines run cooler on synthetic oil, and the oil doesnâ€™t breakdown at high temps. (I do this now.)
If you have a 2008 Sienna with a tow prep package, and know for sure what it consisted of, please let me know. Or if you can shed any light on this fiasco, please do.