mtobeck replied to DHC331's topic in 2015 / 2016 / 2017 / 2018 Silverado HD & Sierra HD Issues, Troubleshooting, & Recalls/Service BulletinsDid anyone find a fix for this yet? Mine just started doing exactly what OP described. 2015 Silverado 2500hd LT 2wd 66,000 miles
Premium is not required by any means on the l96, but it is with the 6.2L. Black bear performance says on their website that these engines don't run efficiently on 87. GM suggests at least 89 for 10:1 compression ratio and higher engines, 9.7:1 is not too far from that. I'd be willing to bet the ecu is retarding timing slightly with 87. I don't know why else I would be getting better mpg with a lower btu/gal fuel. I drive the same drive everyday. E15+88 is essentially 88 octane, so it may be a great option for efficiency and cost per mile with the l96, depending on the price in your area of course.
I remember seeing a post on here about someone suggesting not to run 87 with these engines due to knock, but I'll have to do some digging to find it. Edit - these posts mention it: http://www.gm-trucks.com/forums/topic/187631-run-a-tank-of-91-in-your-60/ http://www.gm-trucks.com/forums/topic/186574-premium-gas-in-a-53l-gmt900/page-2 http://www.gm-trucks.com/forums/topic/171043-what-type-gas-do-you-use-87-89-92/page-3
Hmm. Which could explain the lower mpg with 87. The computer probably detects too much knock with 87 and retards timing a bit, which causes more fuel to be injected. The e15+88 probably has a bit higher resistance to detonation to not cause timing to be retarded as much. Therefore, not injecting as much fuel. Thoughts?
I'm definitely getting higher mpg with e15 than with 87. Maybe it's due to the fact that it is e15+88 (sold at Murphy USA stations). I'm sure someone somewhere has studied the formula of e15+88 and knows the exact BTUs vs plain 87, that would be interesting to know. And btw re-read my post. You're mixing things up. I said e85 cuts down on total miles per tank, and then I said e15 gives much better mpg vs e85, hence more miles per tank with e15. Sorry for confusing you.
I know my truck definitely runs better on e85, but I'm lucky to even get 11mpg with it. That cuts total mileage per tank down by 100 miles and means much more frequent trips to the gas station (if you can find one that sells it). They sell e15 by me and its cheaper than 87 and get much better mpg.
mtobeck replied to joshc64311's topic in 2014 / 2015 / 2016 / 2017 / 2018 Chevrolet Silverado & GMC Sierra 1500I just got my first tank of e15 in my 2015 2500, and mileage is on par with premium 93 octane. The pump said it was e15 + 88 for flex fuel vehicles only. I do a lot of city driving and get about 15mpg with 93, 13mpg with 87, and 10mpg with e85. So far I'm holding 14.5mpg with the e15 and it's a hell of a lot cheaper than 93. It's a little more expensive than e85, but was 10 cents cheaper than 87. We'll see how the truck runs after this tank, then I decide whether or not to use e15 full time. It sure is nice being able to pick and choose which fuel to use.
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