Fuel efficiency drop in newer models ?

[viven44]

I think this is one of the many tricks used to meet the stupid EPA tailpipe emissions. BURN MORE FUEL to have "cleaner" exhaust!

This has been the mojo since the 70s. Engine valve timing was seriously retarded in the 70s to reduce compression ratio/NOx emissions but that really hurt the fuel economy as well, low end torque suffered. These engines with seriously retarded timing sets ran poorly when miles accumulated... what a mess it has been for a long time....

 

[jfoj]

Wait until you monitor the ignition timing vs RPM and Load!!!

If the 5.3l timing map is anything like the 6.2l timing map you will feel the power pulsing or fish nibbling with partial tip in throttle. I think GM screwed this timing map up, I saw this on the early 2000's BMW's they messed up the tip in timing map BIG time. They did offer some DME updates that sorted this out, but on some of the more high performance engines only a few of the good aftermarket tuners figured this out and resolved the timing map problems.

My 6.2l will reduce the timing by up to 30 Degree when tip in throttle is applied in a gear other than 1st or 2nd. You can feel it, seems like the the engine is missing, but it is not, there are power pulses when the timing is starting to advance back when easing out of the throttle.

This is not the greatest capture, but you can see the ignition timing tank in a number of places.

 

[rlhmarines]

This is from our recent trip to Florida over the weekend where we encountered frequent rain showers along the way in our not fully broken in ‘25 Tahoe HC 6.2.

We averaged around 80 mph for the most part with not a lot of cruise control except for some of the more clear skies and traffic. It was getting really good fuel economy before the heavy rains started and this was on trip down but I forgot to take a picture of the return leg’s average mpg.

 

[blanchard7684]

This is from our recent trip to Florida over the weekend where we encountered frequent rain showers along the way in our not fully broken in ‘25 Tahoe HC 6.2.

We averaged around 80 mph for the most part with not a lot of cruise control except for some of the more clear skies and traffic. It was getting really good fuel economy before the heavy rains started and this was on trip down but I forgot to take a picture of the return leg’s average mpg.View attachment 457069

I can get that mpg with my 5.3 if I’m going downhill with wind at rear hatch…

 

[vcode]

This is from our recent trip to Florida over the weekend where we encountered frequent rain showers along the way in our not fully broken in ‘25 Tahoe HC 6.2.

We averaged around 80 mph for the most part with not a lot of cruise control except for some of the more clear skies and traffic. It was getting really good fuel economy before the heavy rains started and this was on trip down but I forgot to take a picture of the return leg’s average mpg.View attachment 457069

1/3 of your time is idling? 51 hours in a nearly new truck?

 

[jfoj]

That's not unusual if you live in a Metro area.

It used to take my wife 45 minutes to drive home 7 miles

 

[viven44]

I can get that mpg with my 5.3 if I’m going downhill with wind at rear hatch…

Makes no sense that the 5.3L is doing worse in fuel economy. I guess we can’t complain at least it gets us from point A to B without needing much TLC and on 87 octane.

All the 6.2L guys are going to need better fuel economy anyway to pay for premium gas and now premium oil

 

[blanchard7684]

Makes no sense that the 5.3L is doing worse in fuel economy. I guess we can’t complain at least it gets us from point A to B without needing much TLC and on 87 octane.

All the 6.2L guys are going to need better fuel economy anyway to pay for premium gas and now premium oil

Don’t get me started…

 

[rlhmarines]

Makes no sense that the 5.3L is doing worse in fuel economy. I guess we can’t complain at least it gets us from point A to B without needing much TLC and on 87 octane.

All the 6.2L guys are going to need better fuel economy anyway to pay for premium gas and now premium oil

I’m a little bit use to paying for premium gas from before with my Camaro ZL1 but the Tahoe has about double the size of fuel capacity. I usually fill up with Top Tier rated gas from Costco 93 octane when I can or Sam’s Club 93 octane which was as low as $2.89 up to recently $3.39, on this trip gas was cheapest at $3.06.

 

[rlhmarines]

1/3 of your time is idling? 51 hours in a nearly new truck?

Congested traffic commuting is the only thing I can think of with the idling time on the trip info page.