Mpg on 2.7t and mods

Sunnyd360 · May 19, 2020

What is everyone averaging? I was worried I would go down with the bigger wheels (24’s) but no issues also if anyone has an intake on a 2.7t let me know if you got better MPG? Thank you all for sharing!

f8l vnm · May 19, 2020

Not sure if last 25 milies is a clear indication of a trucks MPG ..

What is your last 400 miles ?

My 2019 6.2 sierra shows 15.8

Bryant_Olson · May 20, 2020

Not that, but I'm only driving to the store and back. 18.5 or so. But yea, last 25 is not going to be accurate of actual mileage.

Sent from my SM-G965U using Tapatalk

Sunnyd360 · May 20, 2020

Make sense last 400 miles but last couple of months with covid been mostly city

Bryant_Olson · May 20, 2020

Yea, that's more in line with what I'm getting right now. But my trips have been about as bad as you can get for efficiency.

Sent from my SM-G965U using Tapatalk

Jonofmac · May 20, 2020

My 6.2 on a trip from Houston to Dallas. Door to door. 78mph the entire way. Was getting 24 in the 65 mph areas.

Sent from my SM-N960U using Tapatalk

Bryant_Olson · May 20, 2020

My 6.2 on a trip from Houston to Dallas. Door to door. 78mph the entire way. Was getting 24 in the 65 mph areas.

Sent from my SM-N960U using Tapatalk

My 2.7 will average a pretty easy 23-24.5 on a highway stretch like that.

Sent from my SM-G965U using Tapatalk

Jonofmac · May 20, 2020

My 2.7 will average a pretty easy 23-24.5 on a highway stretch like that.

Sent from my SM-G965U using Tapatalk

Only down side for me is that premium is recommended or you lose 2-3 mpg

Sent from my SM-N960U using Tapatalk

Sunnyd360 · May 20, 2020

1 hour ago, Jonofmac said:

Only down side for me is that premium is recommended or you lose 2-3 mpg

Sent from my SM-N960U using Tapatalk

Wait really man I been putting in regular... That’s what the dealer recommended for mine.. I do stick the higher grade has such as chevron or shell

Jonofmac · May 20, 2020

Wait really man I been putting in regular... That’s what the dealer recommended for mine.. I do stick the higher grade has such as chevron or shell

Yup. There was a pretty in depth review by a 3rd party that tested the 6.2 with premium vs regular. They found a relatively minor change in power (they dynoed it) but found a 10-15% mpg decrease from not using premium. Of course premium is normally more than 15% on top of regular, so regular typically is still cheaper cost per mile.

I'm coming from a 2500HD 6.0 that got 10 mpg so even with premium, I'm saving a ton of money

Sent from my SM-N960U using Tapatalk

CamGTP · May 20, 2020

Link to that review?

I didn't gain MPG when I specifically tuned my truck to run on 89+ octane over 87 octane ( for power reasons). The change in octane rating is just changing how resistant it is to ping/knock. If the stoich ratio of the fuel is the same for 87 and 93 octane, what would make the mileage change? The computer doesn't even know what octane you put in the tank, it doesn't even know if you put E0 or E10 in the tank because the stoich value is set to one single number as there is no alcohol sensor. The fuel trims would auto adjust for any minor difference anyway which wouldn't change the mileage.

I've spent many days behind a laptop tuning vehicles and for me it hasn't worked like that for mileage gains/losses by using different fuels not including E85. To lose 10-15% is a ton just because of 87 or 89 octane and that doesn't make much sense.

Jonofmac · May 20, 2020

Link to that review?

I didn't gain MPG when I specifically tuned my truck to run on 89+ octane over 87 octane ( for power reasons). The change in octane rating is just changing how resistant it is to ping/knock. If the stoich ratio of the fuel is the same for 87 and 93 octane, what would make the mileage change? The computer doesn't even know what octane you put in the tank, it doesn't even know if you put E0 or E10 in the tank because the stoich value is set to one single number as there is no alcohol sensor. The fuel trims would auto adjust for any minor difference anyway which wouldn't change the mileage.

I've spent many days behind a laptop tuning vehicles and for me it hasn't worked like that for mileage gains/losses by using different fuels not including E85. To lose 10-15% is a ton just because of 87 or 89 octane and that doesn't make much sense.

Found it.

https://newsroom.aaa.com/wp-content/uploads/2017/12/Premium-Fuel-Phase-II-Research-Report-FINAL-2.pdf

Its a 2017 6.2 in an Escalade, but very similar. 2019+ gets DFM instead of AFM, but I'm not sure if it helps in this situation. Other than that, it's the same engine with the same recommended fuel recommendation.

See there's a 13% difference on flat ground between regular and premium! They also have dyno charts showing power difference. Very thorough testing.

Speeds are lower than I drive. They hypothisized that the huge difference in mpg at 0% grade was due to truck not going into V4 mide as much. I am currently testing this on my own truck to see if there's a noticable difference in certain conditions.

Sent from my SM-N960U using Tapatalk

Jonofmac · May 20, 2020

Link to that review?

I didn't gain MPG when I specifically tuned my truck to run on 89+ octane over 87 octane ( for power reasons). The change in octane rating is just changing how resistant it is to ping/knock. If the stoich ratio of the fuel is the same for 87 and 93 octane, what would make the mileage change? The computer doesn't even know what octane you put in the tank, it doesn't even know if you put E0 or E10 in the tank because the stoich value is set to one single number as there is no alcohol sensor. The fuel trims would auto adjust for any minor difference anyway which wouldn't change the mileage.

I've spent many days behind a laptop tuning vehicles and for me it hasn't worked like that for mileage gains/losses by using different fuels not including E85. To lose 10-15% is a ton just because of 87 or 89 octane and that doesn't make much sense.

Also it makes sense. Look at the SCR of these GDI engines. They're higher than your normal PI engines. GDI allows for better mixing allowing you to get away with more compression, but it starts to become more possible to be knock limited at cruising loads.

Read the article and it shows the difference in ignition timing while cruising. You're correct the cars don't know the octane, but they all have a knock ****** learning vector to allow it to blend between two spark tables. I see it when tuning my vette. Hell, even when I did a heads cam swap on my old truck and tubes that, I had to pull timing from cruising ranges, even with 10.3 SCR. On 93, it got better gas mileage.

You start becoming knock limited.

I've spent a fair amount of time tuning vehicles myself. Mostly gen3 and gen4 GM but I'll use my own truck for gen5 testing. I agree if you're not knock limited, you won't really see a difference, but there are a lot of factors that determine MBT and if you can't get to it because of octane, you'll see a bump in gas mileage.

Also when you tuned for 89 for power, did you bump your part throttle spark? Just tuning wot won't affect part throttle. I normally pick up 5-8% mpg just by bumping spark. I can't necessarily attribute that to octane allowing me to add more timing on most vehicles, but my truck and better both exhibited this.

Colossus · May 20, 2020

Carbon build up on these DI engines is also going to have an impact. The carbon deposits in gasoline engines is tough tough stuff. Make sure you are using good additives IN ADDITION to top tier fuels to treat this. Consider having a professional decarbon treatment done every 15,000-30,000 miles too. I've had great results using BG GDI service. Seafoam might also offer good results. Read up and educate yourselves, and decide for yourselves, but you do need to keep carbon deposits in mind and plan for regular maintenance.

https://www.bgprod.com/blog/gdi-solved/

https://www.knowyourparts.com/technical-resources/chemicals/cleaning-gdi-engine-carbon-deposits/

https://www.delphiautoparts.com/usa/en-US/resource-center/gdi-servicing-dont-let-carbon-build-become-big-issue

https://lucasoil.com/gdi/

https://seafoamsales.com/sea-foam-case-studies-gdi-revival/

Edited May 20, 2020 by Colossus

Jonofmac · May 20, 2020

Carbon build up on these DI engines is also going to have an impact. The carbon deposits in gasoline engines is tough tough stuff. Make sure you are using good additives IN ADDITION to top tier fuels to treat this. Consider having a professional decarbon treatment done every 15,000-30,000 miles too. I've had great results using BG GDI service. Seafoam might also offer good results. Read up and educate yourselves, and decide for yourselves, but you do need to keep carbon deposits in mind and plan for regular maintenance.

https://www.bgprod.com/blog/gdi-solved/

https://www.knowyourparts.com/technical-resources/chemicals/cleaning-gdi-engine-carbon-deposits/

https://www.delphiautoparts.com/usa/en-US/resource-center/gdi-servicing-dont-let-carbon-build-become-big-issue

https://lucasoil.com/gdi/

https://seafoamsales.com/sea-foam-case-studies-gdi-revival/

No fuel additives will stop carbon build up on valves. You have to use a cleaner that you spray into the intake.

Sent from my SM-N960U using Tapatalk