Success

[BHarvey]

My last two tanks were 32 and 34 respectively. This is combined mpg for town/hwy in Atlanta. My 34 was with 44psi and the 32 was with 38psi. The temp had dropped 20+ degrees and tire pressure dropped with it to the tune of 4 psi. So this brings me to a question about tire pressures.

When you adjust pressures to lets say 44psi on a 35F morning and later it heats up to 70F, but without having driven the car, will the pressures now be well over max?

I am aware that a higher inflation pressure reduces the amount of heat the tire generates, and this in turn makes the pressure rise less from 'undriven pressure' to 'driven pressure'.

[sicivic89]

Originally Posted by BHarvey

My last two tanks were 32 and 34 respectively. This is combined mpg for town/hwy in Atlanta. My 34 was with 44psi and the 32 was with 38psi. The temp had dropped 20+ degrees and tire pressure dropped with it to the tune of 4 psi. So this brings me to a question about tire pressures.

When you adjust pressures to lets say 44psi on a 35F morning and later it heats up to 70F, but without having driven the car, will the pressures now be well over max?

I am aware that a higher inflation pressure reduces the amount of heat the tire generates, and this in turn makes the pressure rise less from 'undriven pressure' to 'driven pressure'.

Yes, the pressure will go up when the ambient air temp increases to 70F. Its basic universal gas law PV = nRT. Or P=nRT/V. If the temp goes up, your pressure will go up.

[NHRABill]

crazy how pressure affects mpg so much just a couple PSI = huge MPG difference.

[BHarvey]

Before getting into being serious about saving fuel I had always used cruise, always kept a reasonable speed (with the flow) and coasted whenever I could. My average for severe in town (27) to highway with cruise on 70mph (35.5) netted me an average of 31.2 for ten tanks. My last three were 34, 32 and 34.6 when I filled up tonight. This is combined mpg as I am a courier here in Atlanta.

I was thrilled to get that and that was with engine on coasting when on surface streets and limiting my speed to 60 hwy on cruise (right lane only) and only coasting on the big downhills, and cutting the engine at traffic lights.

This next tank will be a little different as I am going to coast at every chance. Might even limit my speed to 2k rpm's (58 mph).

Now if I could get a weekend off to build the block, get the moon discs, and install some 5x2 inch wide angle mirrors to get rid of the stockers, which are 45+ square inches each......

[BHarvey]

Got 36.2 on my last tank. 35+ combined was my first goal with a stock vehicle so 'I' am doing better. If the mods bring it up a few more I might even see 40mpg combined!

Math is working out to me saving .10+ a mile and I always thought I drove efficient before.....

[BHarvey]

35.2 with the last tank. Four tanks now averaging 35 mpg combined and the car is rated at 35 hwy and 28 combined. Averaging almost 4 mpg better than I used to and it is very addictive....

[nemo]

Always nice to hear about others successes. Out of curiosity what are you driving.

[cgbjake]

Good luck, hope to see another $.10 with your planned mods.

[BHarvey]

Originally Posted by nemo

Always nice to hear about others successes. Out of curiosity what are you driving.

2011 Sonata (manual)

[endurance]

Sounds like some great results, especially for the time of year. Do you have a SGII yet? If not, I'd suspect there's another 3-5 mpg to wring out of that engine still.