Originally Posted By: troyh
Again this is due to the CAFE laws, everything has a Xw-20 spec. It may void the warranty, but how many times does this happen in the real world?
A LOT! I have worked dealer service and been involved in it. Also had an engine fail that was replaced under warranty in the family( Sister's car )about 5 years back now and before the mfg would authorize the replacement they checked the oil change history. Very common despite what some here would have you believe. Other members who have worked dealerships and will confirm this as well( ask demarpaint ).
We even have had members on this very site who have posted about how the car mfg, through the dealer, requested proof of proper oil/filter/time frame and mileage before proceeding with repairs. Not long ago a member who did DIY OC's posted how he had to prove proper maintenance done before Toyota would repair the engine in his 4Runner. Based on the mileage and time he owned it Toyota requested proof of 7 proper OC's. Luckily the guy saved his receipts and was able to show Toyota he had done them and used the correct oil and filters. Had he not the repair was not getting done( not without a big fight at the least ).
Car mfg's do care and do check to see that you have followed proper maintenance procedures when an engine failure occurs. Especially these days. It has really been ramped up vs what it was just 5-10 years ago. If you have an internal engine issue, and you did not follow proper OC maintenance as set forth in the owner's manual, expect to be hassled and most likely lose coverage on the repair. It is just not worth it to mess with these requirements during warranty periods. Repairs are too expensive.
5W20 may be used solely for CAFE reasons as you say. However, that does not negate the fact that is the spec'd oil for the vehicle and that is what you have to use to satisfy warranty requirements. 0W30, 5W30, 15W40, whatever are NOT 5W20 as called for by Jeep in the Patriot. Doesn't mean 30 weight will harm anything it just means you are not living up to your responsibilities to preserve that warranty and as a result you are putting it at risk.