Winter Vs Summer Fuel Mileage

[Brown_Muscle]

Maybe this has been covered..but what are the fuel mileage differences you notice with summer vs winter gas. My wagon seems to consistently get 12-14 in town, and pretty much 18mpg @ 72mph highway. I've only really owned it since they switch to winter blend. I was hoping for better highway mileage (no i cant drive slower, this is NJ!). So i was wondering if these cars are greatly affected by the winter blend gas.

[turbo2256b]

have seen a 2 to 5 MPG difference in part do to cold and in part winter blend of fuel

[Tiggie]

I match your exactly with my 88. I do not notice much difference in summer, maybe 1mpg better town and highway.

This car got 24mpg highway on my first trip home with it (120 miles). It’s never since gotten even close, with 21 being tops on the highway and a very light foot.

I experienced better highway MPG with the 82 and the VV carb, which was 22 pretty easy. In town was much worse though.

[gadget73]

you're getting what I'd expect to see out of that. My Towncar is pretty much the same. The Mark VII is also not much better. It might do 20 on the highway but thats realistically it.

[DerekTheGreat]

I got 24.xxx out of my Town Car doing 65mph at 12 degrees base timing on what I think was winter blend. It was Exxon gas, we filled up somewhere in southern Ohio I think on the third week of February IIRC. This year running it at 10 degrees and 65 best it pulled was 20 or 22 and some change. I wasn't fond of running 12 any more due to pinging under light load conditions. No ping whatsoever at 10. I might try 11 as a compromise.

[turbo2256b]

different areas have different blends for winter

[knucklehead0202]

It's never winter here and i hardly drive my car, lol.

[DerekTheGreat]

Manual states "some ping is acceptable as it means you're getting the most from your gasoline" but I've heard that beats the hell out of pistons & bearings so I'd rather my engine live. You'd never hear it with the radio on so maybe I should just go back to 12 degrees?

[gadget73]

Detonation is not good.

Mine both tend to rattle like mad at anything beyond stock timing, so I have never advanced it. The Towncar has had several engine and ECM configurations over the years, none of them have appreciated anything beyond 10 BTDC. The Mark VII I tried it with once, and it carried on at 12, its absolutely quiet at 10.

[DerekTheGreat]

I like to experiment, figure I'll try 11 and if I get any sort of pinging, back to 10 where it's safe. Almost warm enough to start playing with our mutated VII again...

[turbo2256b]

HAVE FOUND 9 to 14* works just depends on what not really sure. Some thoughts are the water coring in the block and heads. core shift, some core sand stuck in areas. Have also pulled apart engines were the pistons are almost flush with the deck another down the bore a bit same engine year model.
Carbon build up on the pistons, plugs your running. Is there air in the coolant system.

[sly]

The Mad Marquis seemed to love 15*. Though 18 would make it bitch. The Mark VI that sxcpotatos has now seemed to give no cares about anything but ran best for me around 14*. It didn't even gripe about 20, but it wouldn't run well at idle at that point without holding the throttle open a little. I never ran it up the RPM range at that much though. Considering how much dickering was done to that car before I got it, I wouldn't doubt the balancer being a little off.

[sxcpotatoes]

From all the research/reading I have read about it before online, it's claimed that winter gas returns 10% less mileage than summer mix, IIRC. Or is that Ethanol gas = only 90% of the mileage out of pure gas (I know that's true).

[sly]

Winter gas is worse, and I would believe by 10%, but don't know for sure. Gas with ethanol is worse, but only on the order of about 4%. So if you regularly get 20mpg with pure gas, you'll get 19.2 with 10% ethanol.

[DerekTheGreat]

I think part of the problem is also since it's colder out, cars are running in cold enrichment mode for longer, especially for those vehicles effected by short trips and such. My coworker drives a 4 banger Hondoo with a stick but since his commute is about 2 miles, he sees low 20's and even high teens during the winter.