Any easy, cheaper ways to increase MPG?

[Cam2363]

Im looking for ways to increase the MPG on my 96 retta with the GM 3100, I get around 15 mpg currently but would love to get more. Most if not all of my driving is city, I do very very little highway.

I know about the simple stuff, like no hard acceleration and have all the tires inflated properly, but I'm looking for some mods that can increase my MPG, without swapping a bunch of expensive parts out.

Im open to any other suggestions you guys may have!

[Rettax3]

15? That is TERRIBLE! My '95 (old one) gets mid-to-high 30's highway, city only I see around 22, with mid twenties mixed. I know you've done your tune-up work, and keep up on the maintenance. But just to double check, air and fuel filters, good plugs and wires, new PCV valve, run a fuel injector cleaner (premium, like BG44k, something that actually WORKS). A new O2 sensor might help a little too, but could also hurt. Since you have a '96, clean your MAF too, use an actual MAF cleaner, not brake-cleaner or carb-cleaner, and check your intake boot for deterioration, cracks, leaks. Also clean your IAT sensor while you are cleaning the MAF. Then you need to think about tires -aggressive tread works great for poor-weather traction, but something more like a touring-type will be quieter, smoother, and get better MPG. I like all-season tires (my old Z is running Dunlops currently) but if you find a tire that has a solid, unbroken line of tread anywhere on it, that will help you.

Beyond those basics, a cold-air intake might help a little, headers can add efficiency, but are expensive for 3100s. Further exhaust mods won't help city MPG, just performance. My old Z has a modified 3400 intake manifold, plenum, and throttle-body, which woke the car up a lot, but I doubt it helps economy in city driving either, otherwise the car is stock, so you should definitely expect better than what you are getting. Transmission slippage could be a problem too, check the condition of your fluid, since with your mileage it is probably the original fluid. Maybe just do a tranny service, and see how that goes.

Your local gas-stations should be switching over to summer mixes -they have less driers and usually perform better, sometimes have a lower alcohol content too. You may see increased MPG just because of better gas at the pumps soon. Avoid 76 stations, and if possible, any pump labeled with 'MTBE' -not sure if that even applies to your area. Gas should also be getting a lower water percentage in the fuel, due to warmer weather... Experiment with premium or mid-grade gas -my old Camaro (F/I 5.7 liter, five-speed and tall gears for the highway) got 22.25 MPG consistently in the city with 26 highway, and I could get a little better with premium -it made a difference on that car. That was before the CFI manifold swap, but that is a different story...

That is just my set of suggestions from experience. Keep us posted...

[Cam2363]

Thanks. Tires are not an option as they are expensive and I dont have the money.

I used premium once and did go from my 14.8 previous to 15.6 which I was happy about, but not worth the extra 30 cents a gallon.

The one reason I'm searching is gas is up to 3 dollars a gallon so it's like 45 bucks to go from empty to full, which is crazy! And if I fill up about 3 times a month, it's like 140 dollars a month just in gas.

I've been getting about 14 to 15 since I started logging it back in December (I think)

I also run a K&N air filter, and i did the fuel filter and pcv about 6 months ago and the plugs and wires like a month ago. I used NKG iridium's so the plugs should be fine. I also ran a bottle of gum out back in january(see pic) but nothing changed. I can attach my MPG log if you want. Most of it got ruined by some sticky old foam that somehow got in the glove drawer, but I have front like March to now logged. I need to put it in an excel doc.

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[Rettax3]

Hmmm, K&N filter on a MAF-operated car can cause issues. Never experienced them myself, but heard more than once that the oil from the filter tends to atomize off and can bugger-up the MAF's hot-wire, giving a poor reading to the ECM. Definitely recommend starting with that MAF cleaning... Also going to stand by my earlier statement of 'BG44k, something that actually WORKS' -I've never really seen any result from anything else, aside from Wynns' "88k" which I believe is basically the same stuff, I don't think that is typically available over the counter though, online maybe? Been a few years since I dealt with Wynns though...

[Cam2363]

Hmmm, K&N filter on a MAF-operated car can cause issues. Never experienced them myself, but heard more than once that the oil from the filter tends to atomize off and can bugger-up the MAF's hot-wire, giving a poor reading to the ECM. Definitely recommend starting with that MAF cleaning... Also going to stand by my earlier statement of 'BG44k, something that actually WORKS' -I've never really seen any result from anything else, aside from Wynns' "88k" which I believe is basically the same stuff, I don't think that is typically available over the counter though, online maybe? Been a few years since I dealt with Wynns though...

Alright thanks. I will be going tonight to get that stuff.

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[ifixalot]

Switch to synthetic oil. In my 92 Beretta, especially in winter months, I gained 2 mpg by using synthetic.
Oil is thick when the engine is cold. Synthetics have better cold flow characteristics.
Yes it costs more but you can go longer between changes and the better mileage helps it pay for itself.
I been running synthetic in all my cars ever since.

[Cam2363]

Switch to synthetic oil. In my 92 Beretta, especially in winter months, I gained 2 mpg by using synthetic.
Oil is thick when the engine is cold. Synthetics have better cold flow characteristics.
Yes it costs more but you can go longer between changes and the better mileage helps it pay for itself.
I been running synthetic in all my cars ever since.

I already have. I've been running full synth for 2 months now and haven't noticed a huge increase.

[Rettax3]

When I sold my 180+k-mile '92 G/A to a friend of mine many years back, he switched to Valvoline Maxlife -this was before it was a semi-synthetic- and all he got for it was a smoking car. Switched back to conventional, and no problems. I ran Duarblend semi-synthetic in my old Honda 750 -a high-performance liquid-cooled V-4 (yes, V-4)- and noticed a HUGE drop in operating temperature at higher RPMs (sustained running above maybe 3,500-5,000 RPM). Switching several other cars back and forth from synthetics, conventionals, and blends, I've noticed little or no difference in performance or economy. Really interesting how some vehicles respond and some don't. Good suggestion though, ifixalot. You never know what it will do for you until you try it. Some people have reported that the superior detergents in synthetic actually caused worse oil-leaks from their engines too, but otherwise I've never heard anything bad about it, and have used it myself for years too, and yes, you can switch back and forth!

[ifixalot]

In my situation, driving to work, was low slow miles. The engine barley got to normal operating temps by the time I got there.
During winter, my gas mileage was horrible. So I studied up on synthetic oil, (copied text below).
After switching, I noticed a 2 mpg gallon increase in my mileage. Maybe in warm weather you won't notice so much.
Maybe if you get on the highway and the engine warms up, maybe you won't notice so much. I also noticed the engine cranked better during cold snaps. So I conclude the synthetic was not making it harder to turn the engine when cold, which results in better gas mileage in this situation. So I don't think it's a matter of some cars respond better than others. I'm a cheap SOB and I would not spend the extra money on synthetic if I wasn't pretty darn sure of the benefits.

"Conventional motor oils face significant challenges in low temperatures because they contain paraffinic (wax) materials. As temperatures drop, the wax components crystallize and agglomerate into large structures. Eventually, the motor oil gels, becomes resistant to flow and fails to provide the engine with the lubrication it needs. In order to hinder the development of these wax crystals, conventional motor oils are additized with polymers known as pour point depressants. These pour point depressants prevent wax crystals from agglomerating and can lower the oil’s pour point. In fact, petroleum motor oil without additives typically has a pour point of only around 5°F, but the inclusion of pour point depressants can lower the pour point by approximately 25°."

"Synthetic motor oils do not contain the paraffinic material present in conventional motor oils, so they do not require pour point additives. Synthetic motor oils naturally flow at much lower temperatures than conventional oils, maintaining their cold-temperature protection properties over a longer period of time."

[Cam2363]

Thanks for the info, I live in PA so we have cold winters and hot summers. So the synthetic definitely will help in the winters.

Maybe it's just a coincidence, but my current trip is 215 and I am like a teeny bit about E and this has never happened, the most I have ever gotten was about 210 running premium, and this is normal 87. So I wonder if its the summer blend, or my driving habits changed or what it is, but I must say, I am very much scared to drive home today for the fear of running out, but there is a station near my house that has low prices, so I'm going to use that one.

Gas has actually dropped from 2.999 to 2.879 in about 3 or 4 days, which is crazy and awesome!

[Rettax3]

ifixalot, good info there. What is the source, that seems to be a Pennzoil concern, regarding the high percentage of paraffin wax, as that was always the problem with that brand. Works great initially, clumps and sludges badly with age and carbon deposition and loses its' ability to lubricate -I've seen it often enough, any arm-chair mechanic is welcome to their opinion to the contrary, but not with MY engine.

The two main differences I know regarding synthetic vs conventional oils are 1. the detergent levels are much higher in synthetics so they last longer before carbon deposits cause lubrication or viscosity problems and 2. the actual molecule size of the oils are dramatically more consistent in synthetics -which would cause a more consistent flow characteristic for any given viscosity, ESPECIALLY when cold, as you say. Basically, with conventional oils, the molecules 'average' to a certain size, synthetics are engineered to have a consistent size range for each molecule.

Regarding whether or not one engine benefits from this more or less than another, I won't bother arguing about what I have seen, experienced, and what I know, but I'll point out that each engine is designed with different oil-clearances and oil flow patterns and characteristics, each engine was worn-in (or worn-out) uniquely with age and use, and internal friction will have a different effect on efficiency and fuel-consumption between a Chevy 350 and a Toyota 1.5-liter four-cylinder, so different engines SHOULD expect different benefits from changes in oil types. For some, the difference between 'averaged' conventionals and 'consistent' synthetics WILL NOT have a measurable impact, especially if the oil and filter are serviced appropriately anyway. As a note, I lived in a climate that ranged from 100+ highs on summer days to (as seen in my avatar) 27 below zero on a cold winter night, so I also tested in extreme temperatures.

2 MPG is NOT typical results either, but I wouldn't argue about what YOU know and have experienced either, so awesome that you have found a way to increase efficiency that much with such a simple change. What is the actual MPG you get now with the synthetic? How much does it change summer vs winter?

Cam2363, what viscosity oil are you running?

[Cam2363]

ifixalot, good info there. What is the source, that seems to be a Pennzoil concern, regarding the high percentage of paraffin wax, as that was always the problem with that brand. Works great initially, clumps and sludges badly with age and carbon deposition and loses its' ability to lubricate -I've seen it often enough, any arm-chair mechanic is welcome to their opinion to the contrary, but not with MY engine.

The two main differences I know regarding synthetic vs conventional oils are 1. the detergent levels are much higher in synthetics so they last longer before carbon deposits cause lubrication or viscosity problems and 2. the actual molecule size of the oils are dramatically more consistent in synthetics -which would cause a more consistent flow characteristic for any given viscosity, ESPECIALLY when cold, as you say. Basically, with conventional oils, the molecules 'average' to a certain size, synthetics are engineered to have a consistent size range for each molecule.

Regarding whether or not one engine benefits from this more or less than another, I won't bother arguing about what I have seen, experienced, and what I know, but I'll point out that each engine is designed with different oil-clearances and oil flow patterns and characteristics, each engine was worn-in (or worn-out) uniquely with age and use, and internal friction will have a different effect on efficiency and fuel-consumption between a Chevy 350 and a Toyota 1.5-liter four-cylinder, so different engines SHOULD expect different benefits from changes in oil types. For some, the difference between 'averaged' conventionals and 'consistent' synthetics WILL NOT have a measurable impact, especially if the oil and filter are serviced appropriately anyway. As a note, I lived in a climate that ranged from 100+ highs on summer days to (as seen in my avatar) 27 below zero on a cold winter night, so I also tested in extreme temperatures.

2 MPG is NOT typical results either, but I wouldn't argue about what YOU know and have experienced either, so awesome that you have found a way to increase efficiency that much with such a simple change. What is the actual MPG you get now with the synthetic? How much does it change summer vs winter?

Cam2363, what viscosity oil are you running?

I am currently running Valvoline full synth with a 5w-30

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[Cam2363]

Wow. I just got 16.23 mpg, which is my first ever over 16. I'm pretty happy but I want it to be higher. I put a bottle of injector cleaner in and I'm gonna clean my MAF and see what happens

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[Rettax3]

Valvoline is IMO as good as it gets... I've also grown fond of Castrol, both are top-notch products. Only problem I ever had with Valvoline Synthetic was on my '97 Z-24 Turbo -the oil-return into the pan from the turbo was sealed-up with Fel-Pro RTV silicon, as I trusted the name and didn't know then what $#!t their RTV was -the Valvoline dissolved it very rapidly, and I nearly lost the engine due to total oil-loss, thanks Fel-Pro! But that wasn't the oil's fault...

[Cam2363]

Valvoline is IMO as good as it gets... I've also grown fond of Castrol, both are top-notch products. Only problem I ever had with Valvoline Synthetic was on my '97 Z-24 Turbo -the oil-return into the pan from the turbo was sealed-up with Fel-Pro RTV silicon, as I trusted the name and didn't know then what $#!t their RTV was -the Valvoline dissolved it very rapidly, and I nearly lost the engine due to total oil-loss, thanks Fel-Pro! But that wasn't the oil's fault...

That sucks. I had mobile 1 in there before for about a month until I had to redo the RTV on the LIMG and then I used valvoline because it was 5 quarts and a filter for 30 bucks, which was a really good deal

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