Just got back from a four-wheeling adventure in the Bighorns in Wyoming. We took a friends 04 Yukon 8 liter with 40K on it pulling an enclosed trailer with 4 quads and gear. On the way in S.D. we bought gas with 10% ethanol. It got up to 100degrees plus that day. Truck has a trans temp guage that didn't get near the hot mark. Engine temp was fine too. Engine stalled several times at 75 mph. Wait 20 min., start up, drive 20 min., died. Over and over again. At one point when cell service worked, we called a wrecker. When he got there the first thing he asked was " You didn't put any of that ethanol_ _ _ _ in it did you? We limped to the next gas station, filled it with premium and some marvel mystery oil. Ran fine for 1/4 tank or so, died. Filled it again with premium, no mystery oil. Did this re-fill over again a couple more times, diluting whatever fuel was in there. Dealer couldn't find anything wrong. Still the problem. We limped home to Mich. with very little trouble. Can these trucks vapor lock? Anyone had or heard of a bad experience with ethanol? Thanks much, Gus.

 

I occasionaly use a gas that is 20% ethanol and have no problems. Sounds like the ethanol might have been getting too hot and might have started to evaporate in the lines causing air gaps that would cause it to stall. But thats just my opinion.