I have a '94 4Runner and I get pretty horrible gas mileage (12mpg if that), even worse than I have found listed on various websites. Is there anything that I can do to up the mileage? I have replaced the spark plugs and wires and tried a gasoline- engine cleaner (Prolong, or similar). I have heard that a cold air intake could help, or possibly getting a cat-back exhaust. Will either of these help? Please let me know any tips you may have found out. Thanks.
You need to supply more data to determine if 12 mpg truly is bad mileage or not. Urban driving? Highway driving? A mix of the two? Is oxygenated fuel in use in your area? Have you had a compression test of all cylinders in your engine? How many miles are on the vehicle? Does it burn oil? Replace the air filter lately? Lots of short trips (less than 10 mi.) with a cold engine to start? Yadda, yadda, yadda ...
12 mpg would be about par in stop-n-go stoplight to stoplight driving with a relatively short commute to work if you have a lead foot and/or the engine doesn't have enough time to come up to full operating temperature.
There are lots of articles on the web on ways to increase fuel mileage - Google is your friend. Here's a few things you can do cheap:
1) Make sure your tires are in good shape and properly inflated. This is a biggie. Underinflated tires are a big hit on mileage.
2) Aerodynamics are critical. Make sure you're not flapping any body panels, or anything else that might be acting as a drag.
3) Don't drive so fast. *smile*
4) Don't accelerate harder than you need to, and try to maintain a constant speed when you can.
A cold-air intake might help a little, but not much. Do you get any blue smoke? Have you tried checking spark for good voltage and cylinders for good compression? Is your battery in good shape (so your alternator doesn't have to work so hard) and is your alternator putting out good voltage? Is your vehicle shifting smoothly into its highest gear (if automatic) or are you using fifth gear at highway speed? Do you *drive* at highway speed, or is it all stop-and-go? Do you make any long trips or is it all short hops?
Sounds like a V6 with automatic. ADD front hub? If so replace with Warn or OEM AISIN manual hubs -- less moving parts. Use synthetic "oil". Clean injectors with Chevron Techron or better yet send them of to be calibrated. Add a new free flow Cat to the new exhurst and headers.
The aftermarket intake system will give a small hp increase at high rpm and may cost a couple of hp at low rpm...at least that's what K&N's web site dyno chart shows for the Tundra. It'll never pay for itself in gas savings, nor will another exhaust system. If your catcon and muffler are not clogged, there's no economic reason to replace them.
As the others have said, air up your tires, don't hope for good mileage with big lumpy tires, don't carry hundreds of pounds of unnecessary tools and other stuff, and get tune-ups on schedule. Oh, yeah, if you have oversized tires, you're really driving more miles than your odometer shows, so your miles per gallon computes lower than it actually is.
Don't waste money on exotic spark plugs, swirly gizmos for the throttle body, and any of that other stuff--most doesn't work as good as stock, and none of it pays for itself. Don't use 50 wt. oil (15W-50, etc.), do use a top quality fuel system cleaner like Chevron Techron Concentrate. Don't waste money on higher octane gasoline that your truck needs. ARCO gas causes my truck to get about 1 mpg less than Safeway and other cheap gas.
That's your biggest problem right there. An engine is less efficient when cold and half your driving time is in the period where its coming up to full operating temperature. This type of driving is also classified as "severe service" so you should follow the recommended short service intervals for best longevity.
Additional pressure in the tires would help a bit at the expense of a less cushioned ride. If you currently run 32-34 psi, increase it to 38-42 but keep an eye on tire wear. Using synthetic engine oil as well as synthetic in the differentials will also help a bit but only expect a 5% difference.
As another posted pointed out, forget all those whiz-bang miracle gadgets, they'll only improve your mileage by virtue of making your wallet lighter to haul around. Given your driving patterns, I don't think the current mileage you are getting is unreasonable.
Ever consider a motorcycle? A good used 250-400cc dual-sport 4-stroke would run you around $3k and would give you 40-60 mpg in the same conditions.
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