Coasting question M6
09-27-2013, 04:57 AM
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Coasting question M6 After changing plugs and wires on my 2001 SS and netting 0 gas mileage increase from the 20- 22mpg I started driving even more like a grandma. I try to coast more now, however I noticed this car does not gain speed going down a slope that every car I've driven does pick up speed in neutral going down. Is this just how it is with these cars? I don't notice any brake smell or pulling side to side, hit the rotors with a IR and they were all about equal shortly after driving. Maybe those big front and rear tires create a lot of rolling resistance.
09-27-2013, 08:58 AM
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Under what sort of driving conditions did you observe that 20-22mpg? I assume that's not 100% city, since that would be exceptionally good. Even if it's mixed driving though, that's still pretty good depending on the details. If that was 100% highway though, then I'd say it's pretty low for an M6 car.
Is the car stock?
FWIW, I didn't change the stock plugs and wires until about 100k on my '02. They looked great still, and I only picked up a marginal improvement in MPG....barely noticeable even. With a stock engine and properly functioning MAF and O2s, plugs last a lot longer than many people seem to think.
As for coasting, the slope behavior of mine is similar to all other cars that I have driven (speed can be gained on big enough declines, etc.) I have SS wheel/tire size on both of mine, so resistance would be the same as yours. And they are both autos, so any coasting is done in gear (thus more drag than neutral in your M6).
Is the car stock?
FWIW, I didn't change the stock plugs and wires until about 100k on my '02. They looked great still, and I only picked up a marginal improvement in MPG....barely noticeable even. With a stock engine and properly functioning MAF and O2s, plugs last a lot longer than many people seem to think.
As for coasting, the slope behavior of mine is similar to all other cars that I have driven (speed can be gained on big enough declines, etc.) I have SS wheel/tire size on both of mine, so resistance would be the same as yours. And they are both autos, so any coasting is done in gear (thus more drag than neutral in your M6).
09-27-2013, 10:51 AM
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Like RPM said it might be a bad sensor cuz mine(m6) I coast it alot, and I mean alot! and usually have no issues wit neutral rolling for a long distance with little resistance. I'm riding 245/40/17's and 275/40/17's on the rear and I could honestly say the 275 which IMO is too wide for our cars(front).If I coast and neutral i'm getting about 26-27mpg hwy.
09-27-2013, 12:07 PM
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Right now still mostly stock, k&n filter, slp lid, ported throttle body,msd wires, ngk tr55 plugs. Replacing fuel filter and putting on sub frame connectors on this weekend.
Driving conditions I've been getting 22 are being pretty easy with the car, 3/4 highway and 1/4 in town.
Going on what you guys are saying I definitely have something dragging because the one hill I go down I gain up to 5-10 mph and the other stretch I'd hold steady and coast with any other car, the camaro holds speed on the steep one, and loses speed on a slight downhill.
Driving conditions I've been getting 22 are being pretty easy with the car, 3/4 highway and 1/4 in town.
Going on what you guys are saying I definitely have something dragging because the one hill I go down I gain up to 5-10 mph and the other stretch I'd hold steady and coast with any other car, the camaro holds speed on the steep one, and loses speed on a slight downhill.
09-27-2013, 01:13 PM
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When I had a longer commute (75% highway/25% city), I was getting comparable MPGs in bone stock trim. My car is a Z28 with the Y3F factory ground kit and 16" wheels. Original plugs and wires as far as I know (I've owned since 37K miles - now has 96K). As RPM said, plugs don't go bad that quickly unless you've modded the car extensively and not gapped the plugs properly.
As far as coasting downhill, too many variables to consider there. I have 1 of about 5-6 hills near my house that has enough pitch and distance for me to gain speed. Everything else I basically maintain speed, but we're talking about a 40mph zone.
On a pure highway run with ideal conditions (no wind, ~60 degrees, flat roads, minimal traffic) I was able to get 30.3 MPGs (I think - it was 30. something). Best tank in mixed driving is 24.7, and best tank on my new commute (100% city) is 15.2. My new commute sucks for MPGs. I'm the target market for the Chevy Volt.
As far as coasting downhill, too many variables to consider there. I have 1 of about 5-6 hills near my house that has enough pitch and distance for me to gain speed. Everything else I basically maintain speed, but we're talking about a 40mph zone.
On a pure highway run with ideal conditions (no wind, ~60 degrees, flat roads, minimal traffic) I was able to get 30.3 MPGs (I think - it was 30. something). Best tank in mixed driving is 24.7, and best tank on my new commute (100% city) is 15.2. My new commute sucks for MPGs. I'm the target market for the Chevy Volt.
