Economy dropping off - winter diesel?
 

All;

As a rule, will the winter blends of diesel result in a reduction in fuel mileage? Lately my California-spec '85 300TD seems to go through a tankful in far less time (now 310 miles or so and I start watching the gauge much more closely, before it seemed 340 was the norm) than previous, and before I start looking for deeper causes, would like to rule out fuel as a possible culprit.

A search of the forum ID'd several posts related to winter diesel blends, and resistance to gelling, but little on the impact to fuel economy.

Thanks in advance,
Dave

Once the winter fuel arrives, fuel economy drops by close to 10%. The SDL is a good example. I can typically get 29.50 from it in the spring and fall without a/c. The last tank, which included only two cold starts and two 240 mile non-stop runs netted only 27.5. In theory, these runs, at 65 mph (not above), with limited traffic lights (maybe 7 missed lights) should result in fantastic economy. But, they didn't, and the culprit is the winter fuel.

winter mpg
 

When my 220D gelled up at thirty below in South Dakota several weeks back, I was overjoyed to load it up with straight #1 the next day after thawing it and me out.
I suspect cold radial tires does not get significant, if any, credit for the reduced mpg in winter. I'd guess cold radials acct's for at least ten percent of the ten percent.

also have noticed this especially here in the northeast.
i find adding power service white bottle in winter helps on the economy.

I've barely seen any change here in DC on my W123....except for a single week where I obviously got less fuel in on one fillup than I thought my milage has not varied that much since this summer.

I was getting about 31.5 overall in my NA W210 when it was warm out, with the AC running. Now I'm getting about 30, with the same driving. This is normal driving for me, and probably 95% highway, 35 miles each way to work. I can get it just below 30 if I do a few extra cold starts.

So the difference is measurable, but really not very significant for me.

You can use the noticeable performance decrease as a reason to check and possibly adjust your valves.

Never hurts :)

I need to do that myself. I have a new VC Gasket, just need to get the wrenches and the guts to do it!

Hey Ryan!
I agree with Brandon on doing a valve adjustment.....it can really make a difference in the performance of those engines and it can't hurt especially if you don't know if or when the last time it was doneon your 85.
On all my diesels MPG varied from summer to fall then winter. Summer, with AC and all interior environmental controls on was lower than Fall and Spring when I could run in economy mode (AC off). But as soon as winter blend fuel was at the pump the economy would drop a little again. Example of my mileage on 100% highway
84 300SD 27-28 summer , 28-30 fall/spring , winter 27-29 (depending on atitiude) The 300SDL got slightly higher mileage when fuel and conditions were right than the old 84.......31mpg max!
The 98 E-300TD was getting around 34-35mpg this fall with AC off and driving 65. This winter its down to 31-32 if I get a good fill. Winter diesel foams so much its hard to get a good fill and a accurate mpg read.
Happy New Year to ALL!