Ok, my dad recently got a new silverado with the step motor (from v8 mode to v4 mode). He is very dissappointed with the lack of improvement in MPG from his old seirra. They both get the same MPG of about 18 or so. His major issue is that the engine switches back to V8 mode too quickly. I don’t know much about GM ECUs, but I would imagine there are parameters that control when it kicks back into V8 mode. I am guessing the ecu monitors load changes to determine when to switch. I want to know if anyone knows for sure, or how to change these parameters? We would like to increase the amount of load reguired for the engine to switch back to V8. Where are they located in the map? Would a GM dealership be able to do this for him. Also, we would like to be able to get the truck to idle in V4 mode. Any ideas would be great. Thanks
I can’t believe they don’t idle in 4…I don’t think you will find too much info on this. You will need someone who knows the ECU’s inside and out. I don’t think the dealer will help you. A dealer generally won’t edit your computer to your wishes. Maybe try a chevy tuner shop like new era? I know Mike has had to deal with newer chevy ECU’s.
I dunno, I think 18mpg is pretty awesome from a big truck, and the new one getting the same mileage as the smaller and lighter old one is all you can expect. 18mpg from a full size truck in the winter? He should be jumping for joy. I barely get that with my van…But I also dip into VTEC pretty often 
what kind of mpg were you hoping to get?
You should be able to adjust how the ECU handles the V4 mode - just ask someone like Mike@New Era who can do the tuning.
I mean 18 isn’t too bad for a big truck, but when my mom’s suburban is getting the same gas mileage with the older v8 it doesn’t make sense that this new one isn’t doing better, but thanks for the advice I will see what Mike thinks.
arent these engines setup for e85 as well? i was talking with the guys at work and for e85 to actually be efficient enough to put in your truck, it needs to be at least $.50 cheaper than regular unleaded fuel, otherwise your just wasting your money.
i would think you could modify the computer to switch back over, but it would obviously void his warrenty if a gm tech were to do it. i think that if it was possible, gm would have made it that way. then again, the going saying around the dealership is, buy foreign, work for domestic, at least you know your gauranteed to have cars to fix. lol