maverik259

Over the past month my MPG on the highway (only place i really measure) has decreased from around 30mpg to now about 27mpg if im lucky. Anyone have any thoughts as to what might have caused this. I update tire pressure regularly and plugs are only a few months old. Keep in mind this is highway driving at even 65mph at cruise im still only getting at best 27. this is killing me.

phister

have you tried the techron fuel system cleaner lately? injectors might need some cleaning. Have you looked at your air filter also. Dirty air filter will cause loss in MPG sometimes. I'd start with the basic checks, fuel filter, air filter, plugs, stuff like that.

AdidasC230

I really wouldn't consider 3mpg a huge drop, 10 yes 3 no. Different additives for gas will effect gas millage and a 3mpg drop isn't a out of line variance with that. also traffic will effect that, as will many other factors, so I really wouldn't worry that much its not major, it happens

Boom vang

@maverik259
I read your question and the first thing i did was look at your profile at the side to see where you are located. Since you are in Annapolis and not Miami, the drop of 3mpg can be attributed to the change of seasons and as soon as the cold weather or winter is upon us, expect the MPG to drop, it will drop even further if it gets even colder.

pcy

'winter blend' gasoline contains 10% ethanol and possibly other additives may be contributing to the decrease in MPG.

10% of 30 MPG is 3MPG.

ncmudbug

I'm seeing the same thing. I suspect increased ethanol, too. What a boondoggle!

maverik259

well I am not in maryland, I am in Florida. and I use shell nitrogen enriched gas religously. And ya 3-4 mpg is 45-60 miles per tank which is huge in my opinion when nothing apparent has happpened. Traffic is not an issue since i stated that this is based off using cruise control and I've been through winters (even when I was in maryland) and never saw such a decrease in mpg. Sitting essentially empty I would see 29-31 mpg on the highway and now I'm lucky to get 26. I'll try flushing my injectors again, although I remember doing that this summer so maybe its time. And I'll check my air filter although I didn't first think of that because I took taht out and cleaned and oiled it back in October.
Thanks for the replys.

Glyn M Ruck

Check the basics - as others have said winter gasoline can reduce mpg but if you are in Florida then it's not that.

ncmudbug

I have noticed a pretty abrupt decline in mileage. Where I could get as much as 32 mpg going home from work, I now get 27 mpg. My car has a little over 40K miles on it. There is no difference in drivability. Like maverik, I use Shell premium exclusively. I've recently changed my spark plugs and air cleaner (oem paper). When it gets warmer, I'll change the fuel filter. I'll get some Techron and try that, too, but I doubt any of those would make a 5 mpg difference over a few weeks, and certainly not without a difference in the way the car runs. I'm in NC and it's been pretty cold here so I don't discount the possibility of a winter blend that contains more ethanol - for that matter, I discount the possibility that higher levels of ethanol have been mandated year around. I had hoped there would be some notice of a change, but I haven't seen one (they used to post notices on the pump that they are using "oxygenated" fuel but they've discontinued that). I've thought about asking the gas station attendant. Maybe I'll do that.

pcy

just because you live in Florida, please don't assume that you are not using 'winter blend' gas. Check with EPA. 'Winter blend' gas costs more [compared to summer blend] and gives less mpg.

springdriver1

Hey you guys have any suggestions on fuel system cleaners. Or would it be better to go the dealer service an have them do it?

maverik259

techron techron techron

MW_ATL

+1 Techron!!

Autozone had the 12 gallon treatment bottle buy-one-get-one for 7.99 as of yesterday. (vs the 20 gal treatment bottle for 11.99).

cpbeasley

headed there today in that case! thanks man
whats the recommended interval for this?

pwcummings

I had the EXACT same thing happen to me. (See earlier posts). Turned out it was all as a result of gas. I would suggest looking around and finding a gas station that offers "ethanol free 92-93 Octane." I wouldn't trust that going to Shell or Chevron inherently gives you the best gas. I go to a tiny mom and pop owned gas station that literally caters to farmers (they sell farm diesel) and european car drivers, its pretty funny to have my MB fueled up next to a John Deer tractor. But the performance is still 32-33 MPG at 70mph in the middle of an Oregon winter. When I go to Chevron, I get 28mpg at best.

xzstarszx

Wow and I thought all gas are the same (same rating of course). Is this techron stuff the same as the advertised Chevron gas?

MW_ATL

Not really sure. I have dumped the 20 gal bottle or so in everything I have driven about every 3 - 5K miles since, oh...1990 or so. I may just be drinking the Kool-aid, but I've been happy.

I have even done it with cars at work, where after 50K you could actually tell a difference in my car vs. driving a (newer) car with the same miles. However, was the difference the Techron, the having mostly 1 driver, vs many, or driving styles, I can't say. Too many factors.

Yep, same additive. Maybe more concentrated? I don't know about that.

cpbeasley

MW
got myself 4 bottles. was luckily low on gas so I couldnt wait to dump it in. wife's c230 is getting it too. no telling if they had ever been serviced with it.
kool-aid or not, $8-$12 every 5k mile is good peace of mind!

LILBENZ230

Mav.. your car running at optimum temp? I have CEL code P0128 after several days of it just not reaching normal temp and mileage is in the toilet on my C230K. I'm seeing 21mpg in mixed versus 27 and 25 on the highway instead of 32.

maverik259

my temps fine...replaced my thermostat a few months back when i popped that cel...