Why do Gen 7 Corollas lose their great mileage?

[NTL88]

It is common knowledge now that our cars are using more fuel to go shorter distances. My Corolla is using around 10L/100km or 350km (210mi) per 35-40L tank (almost full). It also burns oil. My dipstick goes from full to low in 5 days (300-350km).
What I want to know is where the problem is lying.
After replacing the cracked manifold I gained about 20-30 km per fill-up.
I've already done the ignition tune-up years ago. My next plan is to readjust all belts, change the thermostat, and install a completely new exhaust system (stock or only slightly better than OEM).
I honestly thing its the piston rings, coupled with an exhaust leak.
Any thoughts to share, brothers?

[Kiwi-Corolla]

There are a lot of contributing factors, so it's a good thing that you're planning on replacing your thermostat, exhaust etc. Hopefully you will see some noticeable increases. Worn piston rings could definitely be a contributing factor too, especially since you say that you've noticed your engine using excess amounts of oil.

Also, when changing your exhaust, be sure to inspect your catalytic converter as they can often become clogged and affect your fuel mileage. I've taken mine out as it's not a legal requirement in this country, but I'm not sure what the emission laws are where you live. The engines in 7th gen Corollas were built for economy, but like all things, parts deteriorate in time and cause us to spend more and more money on fuel as the years progress.

As a comparison, my 1.5L 5A-FE engine uses around 37.8L per 550km if I drive it very carefully (with the odd bit of excessive acceleration every now and again). Depending on how heavy your foot is, and what your driving style is, 10L per 100km isn't too bad, but it could be a lot better (as you well know). It's basically a case of trial and error, but I'm sure you'll get there eventually - Just start with replacing the simple things first and you'll no doubt be back to running at full efficiency in no time .

[jelly53]

Also use full synthetic 5w-30....since its thinner and that equals to less resistance which equals to better MPG. BUT since your burning oil badly... thinner oil will burn even faster.....Good Luck!

[PhatRoyale]

Ethanol blends in the gasoline. Winter additives.

More stop and go traffic in Toronto. More traffic lights.

Lack of maintenance upkeep is the biggie. It's definitely the oil burning problem. May be time for a rebuild if you have high miles.

[Hook]

Burning oil is a symptom of worn piston rings, which means you're losing compression on at least one cylinder. Lost compression = lost power, and as a result you have to put your foot into it more to get where u were going at the same rate as before, so u burn more fuel in the process.

With so many more cars on the road now, there's also the issue of traffic which yields 0mpg while you're idling in line wasting precious time and fuel. You're getting 300-350 a tank which is actually not that bad considering the car's age, so I'm assuming you have a fairly long, fairly clear daily commute that allows you to travel at a constant speed.

Also, toping up your oil every 5 days is an added expense that pops up ALOT more often than it should.
It would cost you a bit to rebuild, but it saves u in the long run (w.r.t your fuel and oil bills), and helps you enjoy your ride the way you used to.

[jt14894]

My 1997 CE has been getting great MPG and I haven't noticed any decrease. I can get between 350 to 360 miles to a tank in combined city/hwy
With regards to your oil issue, you may want to have the valve cover gasket as well as the camshaft and crankshaft seals checked. If they're worn, that could lead to oil loss.
I had those replaced in mine and my oil loss has been very minimal. I can go 3000+ miles and not have to add a quart between oil changes.

[NTL88]

Originally Posted by jelly53

Also use full synthetic 5w-30....since its thinner and that equals to less resistance which equals to better MPG. BUT since your burning oil badly... thinner oil will burn even faster.....Good Luck!

Actually, I've just switched from organic 5W-30 to organic 10W-30 and the oil burning has decreased dramatically. From burning overhalf of the shaded dipstick in 350km, I'm now burning less than a quarter of that area in the same distance.

I just bought the Haynes guide today.

[Kiwi-Corolla]

Originally Posted by NTL88

I just bought the Haynes guide today.

Very good purchase! I bought one just after Christmas last year and it has been extremely helpful so far. Worth its weight in gold.

[jelly53]

where can I purchase one?

[Kiwi-Corolla]

Originally Posted by jelly53

where can I purchase one?

There should be some on Ebay, or you can purchase one from haynes.com. The one to get is with the green Corolla hatchback on it, 1992 to 1997.

[NTL88]

I used kijiji.com. I got it used for $15CA. Its sells new for $25CA.

Mine has a gold corolla sedan on it. It applies to 1992-2002 Toyota Corolla & Chevrolet/Geo Prizm.

[Kiwi-Corolla]

Originally Posted by NTL88

Mine has a gold corolla sedan on it. It applies to 1992-2002 Toyota Corolla & Chevrolet/Geo Prizm.

Oh ok, they must have different ones for different parts of the world. I'd assume the info would be relatively the same though, if not identical.