MPG issues

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I own a '95 Honda Accord and the EPA estimates have me at 23 in the city and 30 hwy.

I can agree with that.

It also says that my combined gas mileage should be about 26 or so (which my friend with a 97 does get).

What I want to know is why I'm getting a combined trip of 23 mpg and my friend with the lead foot and A/C gets 3+ more MPG. I don't use the A/C most of the time.

Could the oxygen sensors make that much of a difference if they were worn out? Granted they cost over $300 to replace, so I'd like those to be a last resort option.

The car is in decent mechanical condition.

The tires are at 35psi, just had a tune up ( plugs, cap, rotor button, wires were reused), coolant is good, thermostat works fine, gas is fresh (every 2 weeks), brakes work well, oil is fresh, transmission fluid is new.

The only thing I can think of is that the CV joints are worn, but they don't add that much extra strain on the engine, if at all.

Any suggestions?

Might use Auto-rx on it, but I'll hold off for the moment, since I just changed the oil with M1 10w30 (the car specs 5w30, but it's not that big of a leap).

Thanks in advance.
 
Honda OEM oxygen sensors are always overpriced, and so are many of the aftermarket ones.

You could use a universal sensor instead and get the same results, for about 1/3 the price.

Is the ingnition timing adjustable and if so was it checked?
 
I use Lucas UCL in my car and it gets 5% better mileage when I am using it. I try to use it every fillup but sometimes I get lazy. I do a little better than EPA on my 2002 Chevy Cavalier (combined driving about 33 mpg). Lucas does exactly what it says it will do. Might try BG44K in the tank first to clean the injectors. I would start with the cheap solutions first then replace the O2 sensors if that doesn't work.
 
What kind of spark plugs are you using? Are any codes set? Do you have to have safety inspections where you are? If so, what were your last results?
 
Are your tire sizes the same, with the same wear?
Non standard sizes [or worn] throw you speedometer and odometer off.
 
In my '95 Accord EX 5-spd, 150,000 miles, I've been getting 28.xx mpg for over 2 months, mostly pizza delivery during rush hour. I run my tires at 40-42 psi, and use FP on every fillup. Currently running M1 10W-30 with 1.5 qts M1 15W-50 as makeup oil.

I'm hoping that my mileage will improve a bit more when I get a new clutch installed this coming week.

Definitely do a compression test and let us know the results. I believe that compression should be 178 psi new.

Also, what type of gas do you use? Have you tried different brands? My engine (same as yours) HATES Arco and BP. I've gotten 3-5 mpg less whenever I've run that gas. It likes Chevron and 76 equally as far as I can tell, and seems to run best with a mixture of the two in the tank.
 
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Is the ingnition timing adjustable and if so was it checked?

It is adjustable, but no I haven't checked it yet. I'll look into it.

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If you can, do a compression check.

Roger.

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I use Lucas UCL in my car and it gets 5% better mileage when I am using it.

No change when I use them, but good suggestion.

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What kind of spark plugs are you using? Are any codes set? Do you have to have safety inspections where you are? If so, what were your last results?

I'm using reccomended (stock) NGK plugs properly gapped.

We have safety/emissions checks and everything was far below standard. I did have an exhaust leak, but I patched that up to pass inspection.

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Are your tire sizes the same, with the same wear?

The tires are the same size 205/65/15 (instead of stock 195/65/15), but the the rears are more worn than the front pair. They will need replacement rather soon.

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Also, what type of gas do you use? Have you tried different brands? My engine (same as yours) HATES Arco and BP.

Yo Palut, thanks for chiming in. I use mainly Sheetz or Shell regular 87. Sometimes I'll use cheaper (best deal of the day) gas, but that's hard to find (near me) nowadays (a week ago regular was $1.84 at Sheetz). I'm going to try citgo soon. Also, I am jealous of your 28+ MPG
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Thanks for the suggestions so far.
 
How do you know that your odometer is correct?
Have you tested out on the highway and compared it to the mile markers?
i have only ever had one vehicle that was dead on ...my 1990 Honda Pacfic Coast motorcycle
 
Actually, I've never done the mile marker test.

I have just been hoping that ignorance was bliss.

I'll try that tomorrow though, thanks.
 
I use a portable GPS to check every vehicle I expect to do a lot of travel in. Easiest to take another person along and have them fill in a prepared sheet with GPS-provided versus indicated. Zero can also be set to check odometer. One [old] vehicle I had was off 11%.

Usually good to make several tries at each speed to find consistency.

Also, check alignment, vacuum leaks, brake drag, exhaust restrictions.

Good luck.
 
Is Sheetz fuel oxygenated? I've gotten 2-3 mpg less than expected every time I used oxygenated fuel. As I understand it, Union 76 just recently starting selling oxygenated fuels all over WA. I haven't filled up there since they did that. Maybe I should try...

My car never gets its best mileage on Shell, but it's never particularly bad either.

Have you tried/do you run FP? It gave me about a 1.5-2 mpg improvement.
 
With the larger tires, you are going a greater distance per each revolution.
The Speedometer and Odometer don't know this.
You may be getting 24MPG actually, and reading 23 or so.
 
Is your cooling system working correctly? I had a half-way working motoraid thermostat and never got above 40mpg. I just changed it out with a stant premium and I've never get below 41mpg, normally 42-44mpg. The car runs considerably better also.
 
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Is Sheetz fuel oxygenated? I've gotten 2-3 mpg less than expected every time I used oxygenated fuel. As I understand it, Union 76 just recently starting selling oxygenated fuels all over WA. I haven't filled up there since they did that. Maybe I should try...

I believe that stations around me only use oxygenated fuels in the winter.

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Have you tried/do you run FP? It gave me about a 1.5-2 mpg improvement.

I was going to wait until they had a sale.

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An only slightly out of spec MAF sensor made a big difference in gas mileage in my Audi.

I'm going to test the resistance of the sensor and see if that's the culprit. Gotta pick up a service manual too.

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With the larger tires, you are going a greater distance per each revolution.
The Speedometer and Odometer don't know this.
You may be getting 24MPG actually, and reading 23 or so.

AH. You're right. With the non-stock tire is 2% too slow. When I'm going 60, I'm really traving at 61.2 MPH.

That should account for the MPG I'm missing.

I'm so dumb sometimes.

I'm going to replace the tires back to the stock 195/60-15 size and test it again. The 205/60-15 tires, while softer and all that don't do it for me.

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Is your cooling system working correctly?

It's working perfectly.
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Thanks for everyone's help. With me I always overlook the obvious (I'm a little slow sometimes).
 
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