Poor Fuel Economy with Sub Zero Temperatures

[Fleetw00d]

I drove my 93 EX sedan (stock, auto trans) from Cincinnati, Oh to Rockford, IL (about 430 miles) a week ago. On the trip up, the air temperature was subzero the whole way, bottoming out at -17 F in northern Illinois. I only got about 20 mpg driving at the speed limit. Returning the next day, I blocked the lower bumper opening with cardboard and the air temperature was in the low-mid 20s. I got 29 mpg on the trip home.

Anyone else experience this kind of severe fuel economy loss with extreme cold temperatures?

I know I need to start checking my coolant and intake temperature sensors.

[illinois_erik]

I drove my 93 EX sedan (stock, auto trans) from Cincinnati, Oh to Rockford, IL (about 430 miles) a week ago. On the trip up, the air temperature was subzero the whole way, bottoming out at -17 F in northern Illinois. I only got about 20 mpg driving at the speed limit. Returning the next day, I blocked the lower bumper opening with cardboard and the air temperature was in the low-mid 20s. I got 29 mpg on the trip home.

Anyone else experience this kind of severe fuel economy loss with extreme cold temperatures?

I know I need to start checking my coolant and intake temperature sensors.

ive never noticed, but that week you were also battling strong head winds coming to the ill state, and rode back with tail winds.

[Fleetw00d]

ive never noticed, but that week you were also battling strong head winds coming to the ill state, and rode back with tail winds.

Additional note: The temperature gage on the dash appeared to run in the correct location going up and back (I realize the sensor for the gage is not the one used by the ECM).

I don't remember the wind being such a big issue, but maybe so. After writing the above, I remembered that the check engine light came on a couple times during the trip. I just checked the codes: 12 (EGR) and 14 (IACV). There was a lot of moisture from my exhaust freezing on the back of the car; think the EGR passages could have been cold enough to freeze??

[cb7 calling]

I noticed this year there is a big difference in mpg when its single digit weather. I beleive on the highway the engine is just too cold. I notice when its that cold my heat is warm but not hot, and gets cooler the longer I'm on the highway. Then I'm sweating again once I'm on side streets. Lots of evidence to point to the engine running too cold for efficient performance. I don't think its your egr's froze, I think the ecm just thinks the car is still warming up.

[emosun]

20mpg is normal for any weather so I'm not sure what your problem is , it's not a fuel efficient car to begin with especially when its an automatic.

[Fleetw00d]

20mpg is normal for any weather so I'm not sure what your problem is , it's not a fuel efficient car to begin with especially when its an automatic.

This car has averaged over 27 mpg over the 18,000 miles my family has put on it in all kinds of driving. 20 mpg on the highway is not normal, particularly when the very next day it got 29. Sorry, but if you think 20 mpg is normal for a CB7, then you're the one with a car problem. I used to get low to mid 30s on the highway with my my 93 EX coupe, plenty fuel efficient for me compared to my 99 Ford E350.

[emosun]

Sorry, but if you think 20 mpg is normal for a CB7, then you're the one with a car problem.

The cars original EPA combined rating was 24/coupes 22/sedan 20/wagon.

The majority of cb7's and 9's left are not in very good condition anymore and average the same if not less than their original ratings.

So 20mpg actually IS normal for the average cb7/9 in 2014

let me fix your statement

Sorry, but if you think 20 mpg is the maximum possible for a CB7, then you're the one with a car problem.

[cb7 calling]

If my cb7 averaged 20 mpg I would sell it and take my brothers cd5 v6 wich gets 23 ish. As we are still freezing here in ohio I'm getting about 28 per fill up. That's with some days being single digit like today and some days being 45 plus like it was Saturday. When it's summer my f22a6 five speed clears 30 every fill up. The auto 93 ex I used to have did about 27 mpg in the summer. Apparently honda was not padding the stats with their EPA test cars like their competitors.

[GhostAccord]

Cold air is denser, this causes more aerodynamic forces against the car at highway speeds. It also causes the air to fuel mixture to increase in certain areas of the fuel maps due to there being more oxygen introduced in the dense cold air.

If the O2 sensor sends signals to the ECU that the AFR's are leaning out due to this added oxygen in the mixture. The ECU will add fuel to reach stioch levels (14.7:1 - Air:fuel). It is common to see a slight drop in MPG in colder weather, even more so if your O2 sensor is lazy/dirty/old.

[Ralphie]

Lol at 20mpg being acceptable......

[TheFunk]

I never notice any difference in economy on sub zero days but haven't done a long haul like that in those conditions. Even if it was the same road and same distance, you were headed two opposite directions though so there are a lot of outside factors at play (ie. wind direction, weather, number of stops, elevation changes).

Getting an accurate measure of MPG from only one trip is hard anyways.

And to the naysayers... I run over 30 mph every day on my stock f22a1 with 90 octane and semi-regular use of fuel additives.

[Fleetw00d]

The cars original EPA combined rating was 24/coupes 22/sedan 20/wagon.

The majority of cb7's and 9's left are not in very good condition anymore and average the same if not less than their original ratings.

So 20mpg actually IS normal for the average cb7/9 in 2014

let me fix your statement

Sorry, I don't agree with your fix. My 90 LX with 316,000, the original F22A1, and a Prelude manual transmission still averages about 25 in mostly city driving. All three of my 93s average better than that. 20 mpg overall is not normal, particularly for a tankful of purely highway driving, virtually non-stop at the posted speed limit (70 mph max).

[emosun]

Your 3 vehicles are not the majority , the majority get about 20mpg due to lack of knowledge / maintenance on the vehicle.

Much in the same way if you owned a perfect condition yugo. The majority aren't the same.

At no point did I say 20mpg was acceptable, I said it was normal. There are more bad condition cb7s then good. So bad mpg is now the norm for them.

[GhostAccord]

If I was getting 20MPG for a Sub $3500 car, I would junk it! You are paying more for fuel than it would cost you to buy a newer car.

[emosun]

If I was getting 20MPG for a Sub $3500 car, I would junk it!

I would fix it. But hey some people like to throw stuff away I guess