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1999 corolla
April 20, 2008
Hi I am new to this. This message is for Dave. Just wondering if you got any better gas mileage after installing the blankets over the exhaust manifolds and what was the difference. I have a 1999 toyota corolla, 3 speed auto, no over drive and I get about 25 -30mpg. Gas is now $3.54 per gal in Jacksonville FL and I am wanting better fuel economy. I do the regular maintanance, correct air pressure, rotate tires every 3k miles, oil change every 3k miles, align every 3-5k miles, just replaced serpentine belt, installed k&n air filter. etc.

April 20, 2008#1
The best way to up your mileage to 38 is with a five-speed stick, but since this generally involves replacing the entire car, I'd understand if you didnt want to go that route. I personally found that gas mileage rose a trifle when I overinflated the front tires by 2 psi - improved cornering slightly too. K&N air filter, long term, is harmful - it'll take over 50,000 miles for any damage to occur, though. It lets in some very fine, hard particles that will end up wearing the valve guides, or so I'm told by people in the industry who have examined them. I might be able to dig up some research reports on 'em.

April 21, 2008#2
Hi Dave if that is so for the K &N air filter I guess my engine is toast. I have had it in about 60k miles and the car has 140k miles. Is the damage already done? Should I switch back to regular filters? What about the inline fuel filter? I went to autozone and they do not even show a listing for it. Is this a dealer item only? My fuel filter is a very small black canister next to a green valve for vapor lock.

April 21, 2008#3
As long as you have oiled the K&N filter correctly, damage would probably be minimal. Doesnt hurt to go back to a paper element - I too have a K&N, usually throw on the OEM paper one while the other is getting cleaned and re-oiled. Being running mine for almost 110K miles - so far, so good. UOA (used oil analysis shows low wear and low silicates, the usually sign of dirt penetration). But that may just be a function of the area that I drive around - as they say, your mileage may vary.

The 8th gen do not have an external inline filter - their filter is inside the gas tank, inside the fuel pump assembly. I dont know what black canister next to a green valve you are looking at - but that sounds like the VSV valve for the EVAP system (under the hood, next to the throttle body and air box).

For a 3-speed auto - in mixed driving, 25-30MPG is about ballpark. Like Dave mentioned - only significant way to bump that up is to run a 4-speed auto (overdrive) or swap in a 5-speed stick. Only other thing you can do is lighten the car, getting lower rolling resistance tires or plump up the existing ones with more air, switching to synthetic motor oil and other fluids can help, as far as engine mods - most will tend to worsen fuel economy, than help - so I would stay away from messing with the engine. Toyota ECMs have a tendancy to work around most mods, given enough time. If your upstream O2 sensor or cat is clogged, that could also affect fuel economy. Though better to check them out before one blindly replace them - they could still working correctly.

April 23, 2008#4
Thank you for the detailed reply. Sounds like this is the best I can do short of buying a new used car. or getting a 4 speed auto transmission. Just out of curiosity, have you ever swapped out a transmission and is it better off to have a transmission expert do the job? I wonder what are the costs and if I woould be better off just doing nothing.

April 23, 2008#5
That is a judgement call on your part. A transmission swap is within the reach of most dedicated DIYers and gearheads, but this is a non-trivial swap. Unless you can get your hands onto a half-cut or personally walked to a salvage yard to pickup the parts you need - will most likely run into some major problems.

I've swapped autos for manuals, and manuals for autos - this summer (time permitting), I'm planning a 6-speed swap into the Corolla. Already have about 80% of the parts - just have to make time to do it. You can either support the block and just remove the transmission or pull the whole shot out and work on it outside of the car - both will get the job done, just how much extra work you want to do. Both have their advantages and disadvantages - up to your experience level and how much time you can put into this.

Parts cost-wise, can run anywhere from $850 to as much as $1500 for parts only. If you have a shop put it in - can be anywhere from $1100 to $2500 for the same job - depends on the shop and their experience. Might almost be cheaper to trade in the 3-speed for the same year 4-speed auto or 5-speed stick - your overall outlay of money will almost be the same. Makes the decision that much tougher.

If it is worth it - lets take my typical commute as an example. My commute varies from 80 mile to 200 miles daily. Lately I've been doing about 110 - 120 miles a day, say that works out ot be about 30,000 miles a year. At the worse case for your 3-speed (25MPG - 1200 gallons used) and my average for my 4-speed (35MPG - 857 gallons used), yearly - my savings would work out to around about $1200 (343 gallons saved @ $3.499 a gallon average). If gas hits $4 a gallon, then you are looking at approximately $1374 for that year (30K miles). That almost means that you will have to drive atleast 22K miles to break even with the swap. That is money you have to cough up all at once for a swap, vs sticking with the 3-speed and spreading it out over 22K miles. If you plan on keeping the car for several years - might be a different story. Maybe your fortunes will be different next year - might need to upgrade the car anyways. Very tough decision for many people in the same boat as yourself.

For the swap - dont do it to save gas or get better mileage, that usually ends up being the losing proposition. In the case of popular automatic to 5-speed swaps, it is a performance issue (less driveline losses with a standard shift transaxle).

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