[Efmall]

WOW, my mpg's went up like 17% in the last two fuel fills. I burn about a tank a week.
A few things possibly brought this increase to reality, or one single change or a combination of all.

-The 1st oil change took place two weeks ago with 4k on the car and using Mobil 1 0w-20 advanced fuel economy.
- temps within the last two weeks warmed up. From teens night/ 30's days to 30's to 40 nights/50's day.
-I can't confirm this but, could winter fuel to summer fuel have been phased in during the last two weeks in this area.

Really not sure of why the increase from my avg. of 26.5 mpg to the last two weeks of 31 mpg!!!
It could be the gas, the oil or the temps.
If its the oil, bring it on Mobil 1 love it!:29:
If its the temps, well it's going to get warmer for 3 months then slowly back to winter.:gasp:
If its the gas, I really need to wonder why such variables in efficiencies from winter to summer blends. If we could get a 17% increase in fuel economy year round that could save billions of gallons of fuel!:17:

Very pleased with the recent increase

Any theories on why? It's still mud season here and I thought carrying an extra 50 lbs of mud on the car every day the mpg's would be lower for a while.

Oh, one more thing I just thought of. I don't preheat the car in cold weather very long (maybe a minute or two in winter) but, now that weather has warmed I just wait till oil pressure is up and drive easy for the 1st 5 or so miles.

This is not a complaint, it's a delightful wonderment looking to the gods of forward motion for an answer:1zhelp:

 

[TooSlick]

Factory fill is a 0w-20 synthetic, so that's not it. Id say warmer weather, continued engine break in and possibly a different fuel blend. Your tire pressure will be well above where it was, ie about +2 psi for every 10F increase in temp.

 

[subiesailor]

Temps even in mild california have a big impact on mileage with these cars!

Heck a few weeks back the days high was low 50's the following week it was nearly 70 the mileage shot up in the car too. Went from a weeks tank average of 22.5mpg to 25mpg just with the temp change no difference in the weeks every day driving.

 

[HiPowerShooter]

Actually colder weather can produce better MPG(all things being equal)once the engine is up to operating temp...less fuel to produce equal HP due to air density(VERY important to me as a pilot...not so much as a driver). I'd look at the fuel mix/tire pressure, and engine break in as the likely (good) culprits!

 

[subiesailor]

Actually colder weather can produce better MPG(all things being equal)once the engine is up to operating temp...less fuel to produce equal HP due to air density(VERY important to me as a pilot...not so much as a driver). I'd look at the fuel mix/tire pressure, and engine break in as the likely (good) culprits!

Yes with planes very true. Not so much with all the emissions junk on our new cars.

4gph 190knots at 70%. 600lbs empty. I built one back in the day any guesses?

 

[HiPowerShooter]

Yes with planes very true. Not so much with all the emissions junk on our new cars.

4gph 190knots at 70%. 600lbs empty. I built one back in the day any guesses?

A Vari or Long EZ???

With a Cont 0-200?

 

[HiPowerShooter]

Or a French Cri-Cri...
Oh wait...it's a twin(rotax) and only about 200lb dry!
I first saw one at Oshkosh about 1982 or so...

Funny thing...The same pilot who demonstrated that little thing back then was the chief test pilot(and PIC) for the A380 when it landed at AirVenture a couple of years ago...
Talk about one extreme to the other!

 

[TooSlick]

Fuel efficiency during the warm up phase is a much larger contributor to overall fuel efficiency of passenger cars. For engines that are started and run for hours, not so much.

 

[subaruman49]

The winter fuel mix is GONE in New England !!!!
My car has increased in mpg too !! About 15 % !!!! sometimes 20 !!!

Yea for spring SUMMER !!!

 

[bulwnkl]

Combination of not idling it to warm it up, warmer weather, and probably some break-in/loosening up. Warmer weather includes the potential tire pressure increase TS mentioned.

 

[TooSlick]

Bulk winkle,

Yes, the ideal gas law: PV=NRT

So tire pressure (P) is directly proportional to temperature. Note that (V), tire internal volume is a constant.

 

[subiesailor]

A Vari or Long EZ???

With a Cont 0-200?

Ha ha!!!
Nice actually the Eze the little one. Ironically the Long is slower than the Eze.
We had a super high end shop rebuild an old 100 kinda trick it out a little and set it up to run Auto Gas. So we used the old beater Buick with a couple of 5 gallon jugs in the trunk for the Airport run.
We had 6 Eze's sharing a large hangar only one that could match us was sporting a tricked out turbo Subaru engine. Amazing how much speed loss you get when things aren't built quite square and trim tabs are needed. Our Eze needed so little trim on the test flight the pilot returned snagged my Gramps and they were gone for 4hrs! Came back picked me up and we did another nearly 2hrs. The guy was a Airforce pilot who was one of the primary Eze check pilots in CA. He swore up and down it was the most impressive one he had flown. Showed us with hands off and just both pilots leaning in one direction in the very tight space we had the plane would bank 3degrees either way pending the lean! Awesome experience.

EAA rated it an A+ build helped that my Grandfather was a builder and used a building sight for nearly every aspect of the build. Awesome plane!! Ruined me on the flying thing.
Nothing like starting out flying in one of the fastest most efficient planes ever designed then going and getting in a Cessna and wondering what the **** your doing there. LOL

We flew it pretty conservatively but on a couple occasions my Grandfather pulled off the gloves and shook the cobwebs off his Airforce flying skills. Nothing like playing a little chase over town with a P51D that was insane! Or getting a call from a local static air show for a fly by. Dropping in at 200knots with the hammer down was pretty intense. One of his favorite things to do was to get the call from a local little static air show keeping ears out for planes flying in the area and asking for a fly by. He would say sure be there in a few minutes chat up the planes in the area to make sure it was clear then tell the static show folks he be by in a few minutes when really he was about 30seconds out with the Eze going flat out. You can't see that plane till its right on top of you nor can you hear it so we always got a pretty funny comment from the Static Air show folks about the time we had hit 3200 ft after the fly by. LOL fun times. I think the best comment was "With the radio fed to their PA system asking us to make another pass to confirm it was plane that just went by, then they asked us what our speed was that their fastest fly by of the day had been a T-6 doing 130knots ha ha!!! The Eze flies the pattern at 120 LOL

I need to go dig out the log book I probably have 100hrs stick time in it. Sold it about 12yrs ago, just didn't have the time for it. One day I might pick up a new hot rod kit plane and get back into it.

The really well built Eze's their speed was more or less how much prop they could swing. The prop oddly enough was one of the most expensive pieces of kit we had on the plane. Custom built by a top builder from specs that Rutan sent us. Made it tough to get off the runway on hot days given it didn't bite till we were doing about 50mph. Rotation is 90 so we used a whole lot of runway before the prop started to actually bite. However once in the air that prop was pure magic.

 

[bulwnkl]

TS, I was agreeing with you.

 

[TooSlick]

'Winkle,

I know - but it's not often I get to invoke the Ideal Gas Law....

TS

 

[statueim]

Bulk winkle,

Yes, the ideal gas law: PV=NRT

So tire pressure (P) is directly proportional to temperature. Note that (V), tire internal volume is a constant.

+1 on tire pressure being a factor.

TooSlick, you are assuming tires are a rigid body (or at least a body with a fixed volume) per your statement. Tires are non-rigid by design and share some characteristics with a balloon (think about what happens when pressure is added to the inside of a balloon, the internal volume increases based on the resistance from the balloon's material undergoing elastic deformation and the difference in pressure between the interior/exterior of the balloon). I'm not saying the basic principles of the ideal gas law do not apply nor that the volume changes appreciably where you couldn't consider it's impact as negligible, but volume and pressure both change with temperature to some extent when you are talking tires.

 

[TooSlick]

The plies (steel, Kevlar, etc) under the tire tread and in the sidewalls have a pretty high elastic modulus. So I think we can consider volume to be a constant for small variations in pressure. But technically you're of course correct.

I'd say increased tire pressure could account for perhaps a 5% improvement in fuel efficiency, based on observations with my 2011 Outback.
TS

 

[Looby]

So absolute tire pressure (P) is directly proportional to absolute temperature (T).

There, fixed it for ya.

So, a 10°F delta-T produces somewhat less than 1 PSI delta-P,
(for most automotively-sane ambient temps & tire pressures).

...tire dV/dP = bupkis,

Looby

.

 

[TooSlick]

Looby,

You are of course correct about the temperature part of the equation. However I was trying to keep things simple and illustrate the general principle. It's sort of like trolling for engineers when you post any sort of equation. LOL

TS