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Mon Feb 13, 2012 1:42 pm

i have a 1995 Volkswagen Jetta III GL with the 2.0L 4 cylinder engine. I'm gettin about 30 mpg right now top of the tank highway, but i was wondering if anyone knew any ways for me to improve my gas mileage?

Mon Feb 13, 2012 3:36 pm

Get a diesel :lol:

30mpg is pretty nice out of a 2.0 8V motor. Is your car auto or manual? I drive a MKIII VR6 from Lincoln to Sac everyday for work and manage 28-30mpg depending on traffic. It all depends on acceleration and lots of coasting when applicable.

Tue Feb 14, 2012 12:32 pm

I know i want a diesel really bad, but unfortunately do not have the funds here at the moment. I mainly use my car to get from my school, UTI to my home which is only about a 10 minute freeway drive. It's a manual =D i used to manage about 31, but recently the fuel economy just isnt as good as it was, even though im pretty on myself about air filters, oil changes and spark plugs/wires. You get 28 with a vr6??? jealous

Tue Feb 14, 2012 6:02 pm

thomaslaurie93 wrote: You get 28 with a vr6??? jealous

It has forced induction cams in it even though I took the supercharger off. That may have something to do with it.

Thu Feb 16, 2012 8:36 am

You can always try to do a simple tune up, clean the throttle body. I heard that if you put 93 octane in you might get more, I am in the process of testing this.

Thu Feb 16, 2012 3:27 pm

po7g wrote: I heard that if you put 93 octane in you might get more, I am in the process of testing this.

Maybe in Indiana but here in California, finding 93 is almost impossible and would cost a fortune.

Thu Feb 16, 2012 9:18 pm

I really don't think the higher octane would help much other than give the gas station more money... probably not enough gain in MPG to offset the cost, but you never know. Anyway, that's pretty good gas milage - the 2.0 engine is a good engine - VW never stopped making it even though it disappered for a while in the US market (finally making a reappearance last year on the base-model Jetta, which was immediately pissed-on by the auto magazines as "some out-dated 20 year old engine" - my opinion is more like "a solid well-proven engine with a good balance of economy vs power" but if it doesn't go from 0-60 instantly, it's a crappy engine if you're an auto reviewer.

Other than the normal tune-up issues, and checking your computer codes (these have so many piddly things that turn on the check-engine-light that people just ignore it, then the light bulb often just burns out over the years, if that's the case you might have some issues you don't know about) and changing the air filter, I think I'd be happy with 30MPG. My 85 1.8 Golf seldom gets that good if I'm trying to go 75 on the interstate with all the hills and wind I have to deal with here.

-Andy

Thu May 03, 2012 9:55 pm

I improved my mileage by siphoning a gallon out of my neighbors tank. :lol:

Fri May 04, 2012 1:15 pm

I hope you are joking. I strongly dislike thieves.... [-(

Sun May 06, 2012 9:21 am

Yes it's a joke

Mon May 07, 2012 11:10 pm

:wink: Sweet

Tue May 15, 2012 11:10 am

1. Higher octane: Myth. High octane gasoline has the same amount of energy as low octane gasoline. High octane only helps if your engine pings (metalic rattling sound caused from gasoline spontaneously combusting) since it tolerates heat better without pre-igniting.

2. Tire size: Fact. The wider the tires the more friction. I noticed a change from 47 MPG in a 1991 Mazda 323 I had to 43 MPG with snow tires. I expect the same to happen to my Golf.

3. Making the engine intake breath better: Myth. Unless it's a diesel or carburetted, having more restriction on the intake actually could increase fuel mileage. With modern fuel injection the fuel metering responds directly to the amount of air entering the intake reguardless of the restriction. Besides, the biggest restriction in the intake system is the throttle plate. And we all know you will get better mileage the more you keep it restricted.

4. Advancing the timing: Fact. Ignition timing on many vehicles, especially older ones, is usually more on the conservative side. In a 1995 I'm not sure how close it is. I'll bet that in that year it is pretty close. Even then, if you had the means to do some testing (e.g. dyno) and know how to change variables for compensation for load, RPM, temp, etc then you could program these in to get even better efficiency. With distributors you have to adjust the weights, springs and tabs to get the right curves.

5. Driving habits: Fact. Power = Velocity^3 x Area x Coefficient of drag. The faster you go the more drag you get. This rises exponentially. In one study I read nearly all cars, from big V8's to subcompacts, would get about double the mileage they get at 55MPH if they were driven at a steady 30MPH. Of course jack-rabbit-starts and heavy breaking also use up fuel. In many modern fuel injected engines the fuel is actually shut off when you let off the accelerator and coast with the engine in gear. The fuel comes back on as soon as RPM's are near idle or when you step on the acclerator again.

6. Cleaning and repairing vacuum lines, intake, sensors etc.: Fact. Vacuum leaks are one of the greatest causes for inefficient engines. Also on EFI engines, a dirty MAF sensor will give poor readings for the ECU. Modern engines are designed to run efficiently with properly running PCV and EGR valves. Sometimes removing them only hurts the engine. It was on early engines that they caused problems since they were a new technology not fully understood back then. If you see that "check engine soon" light come on you better get it fixed if you want better mileage. On carbureted engines the best way to accurately tune them is to put on an O2 sensor and guage and then jet it so that the mixture is allways optimal.

7. If you want to get into real efficiency then major changes will be needed like changing the engine to a diesel ICE (internal combution engine), atkinson cycle ICE, miller cycle ICE, gas turbine engine, stirling cycle engine and/or by adding a hybrid electric motor. Also by improving the aerodynamics by making fiberglass or carbon fiber fronts and backs for your car that are more aero dynamic than your stock vehicle shape. Lightening the vehicle with parts made out of carbon fiber, aluminum, titanium and magnesium will also help, especially in stop and go traffic and for going up hills. Other alternatives would be to use alternative fuels like electricity (EV), bio-diesel or wood gas. Of course these all depend on your wants and needs. One person in L.A. told me that she was saving $800 US dollars a month in fuel with their new Leaf EV. Another guy here in town says he spends about $0.60 US dollars per gallon making his own bio-diesel. I spend about $10 a week on fuel with my Golf since most of the time I use my bicycle.

Tue May 15, 2012 11:22 am

Some valid points but as far as octane and timing on an ABA 2.0 engine, with Motronic fuel injection and 10:1 compression ratio... the computer handles all the timing based on many variables, and you can't just simply advance the timing. The distributor has no advance itself, it's all in the computer. Octane, well the computer compensates for lower octane by listening to the knock sensor... so higher octane might help it run a little bit better but will it translate to better fuel economy? Like I said before, probably not much.

Tue May 15, 2012 12:00 pm

glutamodo wrote: the computer handles all the timing based on many variables, and you can't just simply advance the timing. The distributor has no advance itself, it's all in the computer.

Exactly. But even with digital timing the exact timing events can be custom taylored to as optimal as possible. The better the timing advance curves, initial and total are all accurately adjusted the better the efficiency will be whether that be with a regular distributor, a CDI system or a distributorless digital set up of whatever type. Of course once your timing is perfect in every way possible there isn't much more a guy can do as far as timing is concerned. On older cars the timing is almost always on the retarded side, so advancing the curves and all will improve efficiency. Of course many new cars since the 1990's already have optimal timing with the use of a knock sensor. But still if you were to make major changes like increasing the CR or doing twin sparkplugs then you will have to reprogram to get the best timing as possible for the new characteristics of your engine.