Solara's Fuel Consumption Accuracy

[HomeboyMI]

I have a 4 cylinder and the computer says 31 but the calculations come up with 29 country, hilly California driving.

[cronikles]

I have a manual 4cyl. On the highway alone, i get around 31-32 mpg. I don't know what i get in the city, by my overall average is around 28.4 mpg. (This is with 60% highway, 40% city) Very satisfied with those numbers. My problem with the computer is that the "miles left" is always off....by a lot sometimes. If i drive 2 miles (on the highway where it is more consistent), it will read that I have gone 3 or 4. I dont know how you can trust your gauge, Jewls.

[Jewls]

Well, I never let it go below 1/4 tank, so I don't really trust it per say.

[cronikles]

For the poeple with aftermarket wheels, how has your mpg changed with the new wheels?

I have 20" wheels, but my reading isn't too reliable since I just put them on. At times (like highway driving) the mpg is the same or better than stock....at other times, (city driving) its a little worse.

[Animal]

Cronikles,

I would think that by putting 20" wheels, you're going to have a helluva time determining your actual mileage. Primarily because even using a lower profile tire to compensate for larger wheel size will change the diameter at least a little. Your odometer is probably reading too few actual miles now, and it will be difficult to determine by exatly how much. There are calculators available but you'll have to know the original diameter and the new diameter for both setups.

In addition (generally speaking, of course) bigger wheels add both weight and friction (more surface area if you go to wider tires) which both decrease mileage. Unless your 20's weigh less than stock. I think larger wheels will make the computer think you're getting worse mileage since it thinks you're travelling less miles.

The following is from http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm :

Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner's manual.

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars.

Don't throw your money away on higher octane than specified. Toyota calls for 87 and nothing higher will improve HP, mileage or engine life.
<My $0.02 worth - and I know some of you will swear I'm wrong, but talk to any gasoline engine designer... higher octane is for different compression ratios, different engine materials, etc.>

[mmcdonald]

Folks,

Are you resetting the computer after each fill-up? I find that mine is accurate if I do that. If I rely on fule economy over the life of the car, I am never going to match what the computer says on a particular tank. Just hold down the display button for more than a few seconds and it resets. Do this every tankfull.

I did a trip from Baltimore, MD to Wilmington, SC and got 30.5 mpg.