A little background here. Last week, my brother in law and I drove back from Park City, Utah to Idaho - a distance of 730 miles or so. On the way back, our '97 averaged 14.2MPG and his '93 averaged 16.1. Conditions were steady state cruising at 78/79mph the entire way with the cruise engaged.
Mine has 150,000 miles, synthetic throughout, very recently tuned up, very recently had throttle body cleaned, valves and head cleaned etc as part of the head gasket replacement. We both had similar tire pressures and we are both running Michelin's top line SUV studless tire though his are 275 and mine are 265. We probably weighed 200lbs more owing to the extra child and his car seat plus the extra stuff on the 95+ models (insulation, airbags, etc).
His turned over 300,000 miles on the trip and has had casual care and was tuned up a year ago by me.
Here's my question. The only difference I can think of is that I have my engine timing advanced 4 degrees and he does not. Do you guys more familiar with the engine management aspects feel that I end up using more fuel due to this? I'm thinking this wouldn't make the difference.
The reason I'm looking for input is that there is only one other explanation and that is we always run ours in PWR mode and he *thinks* they did not have this engaged on the way home. If you guys think the timing advance issue would make such a huge MPG difference (that's 13 freakin percent better MPG!) then I'll change it back in a heartbeat. If you think it's the PWR mode then obviously that baby's coming off.
So, focus on the timing issue and whether you think that would be it. If that cannot be supported then by default it's going to be the PWR button. Cdan recently talked about this in another thread from the perspective that the engine revving more simply consumes more fuel in ratio to the increased revs and I tend to agree that's it. But I'm interested in the timing advance comments, really.
Thanks!
Informationally, I don't think the head gasket operation changed the fuel economy at all. It's always gotten this mileage on the highway, just that I've never had a 300,000 mile 80 to directly compare and it was a bit of a shocker.
DougM
Mine has 150,000 miles, synthetic throughout, very recently tuned up, very recently had throttle body cleaned, valves and head cleaned etc as part of the head gasket replacement. We both had similar tire pressures and we are both running Michelin's top line SUV studless tire though his are 275 and mine are 265. We probably weighed 200lbs more owing to the extra child and his car seat plus the extra stuff on the 95+ models (insulation, airbags, etc).
His turned over 300,000 miles on the trip and has had casual care and was tuned up a year ago by me.
Here's my question. The only difference I can think of is that I have my engine timing advanced 4 degrees and he does not. Do you guys more familiar with the engine management aspects feel that I end up using more fuel due to this? I'm thinking this wouldn't make the difference.
The reason I'm looking for input is that there is only one other explanation and that is we always run ours in PWR mode and he *thinks* they did not have this engaged on the way home. If you guys think the timing advance issue would make such a huge MPG difference (that's 13 freakin percent better MPG!) then I'll change it back in a heartbeat. If you think it's the PWR mode then obviously that baby's coming off.
So, focus on the timing issue and whether you think that would be it. If that cannot be supported then by default it's going to be the PWR button. Cdan recently talked about this in another thread from the perspective that the engine revving more simply consumes more fuel in ratio to the increased revs and I tend to agree that's it. But I'm interested in the timing advance comments, really.
Thanks!
Informationally, I don't think the head gasket operation changed the fuel economy at all. It's always gotten this mileage on the highway, just that I've never had a 300,000 mile 80 to directly compare and it was a bit of a shocker.
DougM
