Tire pressure set lower, MPGs went up? (Winter thread) - Fuel Economy, Hypermiling, EcoModding News and Forum

101Volts · 11-26-2013, 05:20 PM

For most of the trip legs out of 11.7 miles today, I was getting rather low MPGs partially due to high tire pressure (About 55) and then I stopped at the gas station and set the tires to 46 all around; Then, For the trip home I got the highest MPG figure all day and I did feel more confident about accelerating at higher engine loads; It also helps that I can accelerate at all since I had trouble going up hills earlier! However, This isn't an A-B-A-B test on the same leg of road. But, I thought I'd share the thought.

Daox · 11-26-2013, 05:26 PM

According to Darin's testing, 46 to 55 psi shouldn't make a huge difference is rolling resistance (obviously it differs from tire to tire, but still should be an okay general rule). I'd be more likely to blame a tail wind or something.

http://ecomodder.com/forum/showthrea...tire-2721.html

some_other_dave · 11-26-2013, 05:53 PM

There's a reasonable chance that it was something else that changed and improved your mileage. But it's worth a re-test, I think!

-soD

jakobnev · 11-26-2013, 06:10 PM

Engine temp with the candlestick in the dining room?

101Volts · 11-26-2013, 06:40 PM

Yeah, It's far from A-B-A-B testing and the van started at about 30 FWT. Though I can say with 55ish PSI, I did not accelerate very well in that snow with the methods I tried and setting it to 46 gave it more traction and it made it feel about the same as the day before.

And jakobnev, I'm not sure what you mean.

aerohead · 11-26-2013, 07:04 PM

According to published findings by SAE,an automobile is not fully warmed up until after 22-miles of continuous operation at 50-mph.Only then can you BEGIN testing.

Mad Adder · 11-26-2013, 07:59 PM

High tire pressure and wheel slip in the slick weather, or didn't you get what we got in NEPA?

ksa8907 · 11-26-2013, 09:36 PM

Quote:

Originally Posted by aerohead

According to published findings by SAE,an automobile is not fully warmed up until after 22-miles of continuous operation at 50-mph.Only then can you BEGIN testing.

This.

I've been keeping an eye on my fuel usage per hour at idle, and I don't drop to regular summer usage until after 15 min of coolant being 190+. Engine oil temp is my suspect.

bestclimb · 11-26-2013, 10:53 PM

When I was running winter tires on my civic years ago I would get some wicked wheel hop while spinning due to ice and snow at 55psi, dropped it down to 45ish and the wheel hop went away. Traction during a slide may have gone up (butt-o-meter not any skid testing) but I did not note any significant difference in traction while not skidding (which matches the science I have seen regarding tire pressure and traction). Nor did I note any mileage change as during the winter road conditions and driver technique totally wipe tire pressure rolling resistance changes away.

101Volts · 11-26-2013, 11:50 PM

Quote:

Originally Posted by aerohead

According to published findings by SAE,an automobile is not fully warmed up until after 22-miles of continuous operation at 50-mph.Only then can you BEGIN testing.

I didn't know that, Thanks.

Quote:

Originally Posted by Mad Adder

High tire pressure and wheel slip in the slick weather, or didn't you get what we got in NEPA?

I did get slushy roads, The whole slipping thing is partially due to inexperience and, Frankly, Learning the hard way.

Quote:

Originally Posted by ksa8907

This.

I've been keeping an eye on my fuel usage per hour at idle, and I don't drop to regular summer usage until after 15 min of coolant being 190+. Engine oil temp is my suspect.

I'm now wondering if I should add more to the grille block.

What are some suggestions for engine insulation? I think Frank Lee made one out of styrofoam.