6.2 owner ready to jump ship to 6.6 gasser

[Chuck FB]

2 hours ago, kevin74 said:

 I normally use a mix of 87 and 92, depending on which I feel like buying at the time. I haven't really seen a difference between the 2. I am not sure what the ethanol content is as I usually only worry about that with the lawn mower and atv's. My "normal" gas mileage is around 14 with stop and go traffic, I can get into the 20's (22 showing as best) when on longer highway and interstate trips. I don't get on the gas leaving stop signs or red lights, and I don't idle a lot. 

I am certainly no expert when it comes to the contents of fuel and be that not only the ethanol aspect but additives that some fuels claim to have which may burn cleaner to cause less deposits as well as cleaning the injectors etc and have a feeling there are some in this forum that have more of a chemical background or peers that were in the know of fuels. Having said that I get the impression from certain experts in articles or videos that for engines that don't need the higher octane fuels, its a waste to use high octane if all else is equal additive wise between the two fuel octanes and may even give slightly poorer mileage or stay the same. I don't believe higher octane fuel contains more btu's, its the burning characteristics that are different and not only in preventing preignition on a high compression engine but its burn rate is slower. In modern gas engines if the engine is set up to run regular and the electronics are as well, I don't believe the engine can capture that gain as its not allowing a further advancing of the timing and why an after market tune would advance the spark timing to gain power and then require premium to prevent preignition. 

 

Never the less you certainly can try tanks of 87 only or 92 only, and see what if any difference it makes but I suspect the cost of 92 is not worth it for a non tuned L8T, but as Lineman found out, using 87 no ethanol if the price is right is this engines best bang for the buck.

[Chuck FB]

2 hours ago, newdude said:

 

 

21-24.  

 

And 6.2s have been on the down trend at the wholesale auctions prior to the recall due to them locking up in the first place.  Even the 5.3s had dropped for some time but those have stabilized.  6.2 on the other hand keeps dropping due to the recall now.  

Whats your take on a chance that those who are running regular in the 6.2 are potentially causing damage to the engine by way of dancing on the line of slight preignition ?

[Chuck FB]

2 hours ago, lineman1234 said:

Hear in upper Minnesota, it/87 octane gas, can be 10-15% ethanol, but law, limits it to 10% in the winter time. 

    Last year when getting the pickup from new i did multiple experiments, as well as multiple tanks, on different fuels just for the heck of it. 

 

   Summer fuel only. For less argument, im not posting miles per gallon just my gain. Starting from normal 10-15% ethanol 87 octane at the pump. Trying 91, not sure if its ethanol free or not, i gained 1mpg per tank/s solid, not worth the extra .50 cents  more a gallon. Finding non ethanol 87 octane not far from hear, multiple tanks gained a solid 1.5-2 mpg. Cost changes, some times, lower some times  more than another station with only ethanol. 

 

Wile spending a month last winter in New Mexico, in that area it was 86 then 88 then 91 at the pump choices, the lower 2 had ethanol. Going 88 from the 86 was a solid .75 cents more a gallon. I did try the 86, it ran fine, no noticeable difference, but i lost a solid 1mpg per tank from 87 ethanol. 

       

         

Those are some very interesting results and like you said the 91 octane was a mystery as to if it contained any ethanol or not so if that was due to containing a bit of ethanol or just its slower burn rate over the 87 non ethanol that beat it in efficiency. I think there is a misconception that high octane fuel is somehow a better quality fuel and will magically get better fuel mileage with it when lets say the engine only requires regular to run properly. That was one of the reasons I leaned towards the L8T because it was tuned to run on regular because that is what I have by far more access to and premium is stupidly priced up here anyway. The Ford Super Duty with the 7.3 is said to be ok to run either but gets its power rating from premium, and the GM 6.2 is really designed around running premium period ( and perhaps not so bad that I passed on getting one in hindsight anyway ).

 

Going by the octane numbers you had to choose from in New Mexico, I am guessing that was at a relatively high elevation area, what area was that by the way ?, I've been through a bit of NM quite a few years ago and once was during the winter but that was in the southern part of the state, while summer time was in both the northern and southern part as obviously they get hit with winter in the northern high country. At higher elevations it just seems that engines don't do as well economy wise or I haven't found it to be so with whatever gas truck I was driving, probably that lack of air vs the low elevations and certainly with a carb engine.

[newdude]

3 hours ago, Chuck FB said:

Whats your take on a chance that those who are running regular in the 6.2 are potentially causing damage to the engine by way of dancing on the line of slight preignition ?

 

 

IMO, with how on the edge they keep pushing these on 87, I say 89 or higher.  

[No F-bdy Bs]

Take it to a dealer, let them "inspect" it, and either way you get a 10yr/150k warranty. 

 

My issue with the whole 6.2 debacle is the high likelyhood that you'll NEVER get a replacement 6.2 as there's no way Gm can source enough engines in a timeframe anywhere near reasonable. 

 

Myself, I'd lean on the dealer to do better on trade since they've obviously effed the customer. 

[rdonarski]

On 5/12/2025 at 10:29 AM, Chuck FB said:

I am certainly no expert when it comes to the contents of fuel and be that not only the ethanol aspect but additives that some fuels claim to have which may burn cleaner to cause less deposits as well as cleaning the injectors etc and have a feeling there are some in this forum that have more of a chemical background or peers that were in the know of fuels. Having said that I get the impression from certain experts in articles or videos that for engines that don't need the higher octane fuels, its a waste to use high octane if all else is equal additive wise between the two fuel octanes and may even give slightly poorer mileage or stay the same. I don't believe higher octane fuel contains more btu's, its the burning characteristics that are different and not only in preventing preignition on a high compression engine but its burn rate is slower. In modern gas engines if the engine is set up to run regular and the electronics are as well, I don't believe the engine can capture that gain as its not allowing a further advancing of the timing and why an after market tune would advance the spark timing to gain power and then require premium to prevent preignition. 

 

Never the less you certainly can try tanks of 87 only or 92 only, and see what if any difference it makes but I suspect the cost of 92 is not worth it for a non tuned L8T, but as Lineman found out, using 87 no ethanol if the price is right is this engines best bang for the buck.

I have 2 friends who are into drag racing at a professional level. They both say using a higher octane than what is specified by the manufacturer is a waste of money. I know one drives a newer corvette as a daily drive and uses 87 in it. My last pickup had a 5.3 and required 87 but knocked if I didn't use premium, so I always used premium. I use 87 with my 6.6. Hard enough trying to slip the fuel bills by my wife. 

[EXSlider400]

On 5/2/2025 at 4:01 PM, dieselfan1 said:

I have a 23 High Country 6.2 with 48.000 miles and with all the failed lifter talk and now the big recall, I think I'm ready to walk and get a 6.6 gas.

Diesel is not for me. Used to be a long time ago though. 

Probably looking at an LTZ with the LTZ premium package. Not much difference between that and a HC.

 

I do tow a cargo trailer and a 25 ft travel trailer so the 2500 would be beneficial but I also plan to daily it.

Mpg isn't a big deal to me either.

 Talk me into doing this. Or talk me out of it.

 

made the switch this week  even with the lower MPG, at a dollar less a gallon where I live, it was worth it. 

Edited May 16 by EXSlider400