Your favorite car mod for mpg??

[y2kbug]

Whats your favorite and/or most beneficial modification you have done to your car to get better fuel mileage?
I know there is already the 65+ efficiency mod page that kind of answer this question but I'm more interested in your personal opinion and experience.

I started trying to save more gas when i bought my dakota. By putting skinnier tires on it and changing my driving style i was able to maintain a pretty constant 6-8 mpg gain. Unfortunately i am unable to do any better than that.

Since i bought my 1999 corolla ive been fixing and improving things on it in my free time. Just by replacing the old o2 sensor on it i have gained ~10mpg! I have done a few other things on it but it is too soon to tell what effect it has made.
I'm looking to do some modifications on my vehicles to improve their fuel mileage. Thanks!

[freebeard]

By putting skinnier tires on it and changing my driving style i was able to maintain a pretty constant 6-8 mpg gain.

I put 145s on the front of a 36HP Beetle.



When I aged out of the employable cohort, I went from doing 90MPH on I-5 and passing trucks on the right, to sticking to the right lane and being slower than the trucks.

I'm looking to do some modifications on my vehicles to improve their fuel mileage.

The ultimate mod is a boat tail; but they're a pain in the.... parking space.

[Isaac Zachary]

For fuel mileage? It was buy a 1985 VW diesel and keep the RPMs low and floor it for a "pulse and glide" technique. I'd get over 50mpg on the highways. One trip I did just about 600 miles but couldn't get more than 10 gallons into the tank. The car was also immortal. 3,000 mile oil changes and it just wouldn't die even after who knows how many miles. It had at least 300,000 miles on it, but the odometer was broken and I drove it for 7 years. The next car I got I did 30,000 miles that year, and I assume I drove about the same in that Golf, so 7 x 30,000 = 210,000 + the at least 300,000 miles meant it had over 500,000 miles on it. And that's the lowest guess, it probably had a lot more on it.

Advancing the timing on my 1993 Mazda 323 also was a big help. That, and again, stick shift that I keep the RPM's as low as possible, but in a gasser you keep it mostly floored, but not all the way. The AFR gauge I put on the 1972 VW Super Beetle helped me keep my foot into it just before the enrichment circuit would activate. In all of these cars I'd usually be in top gear at around 25mph. The Mazda got around 45mpg on the highway.

The 1972 VW Super Beetle was the most fun, even though it got the worst fuel mileage. I got a custom cam grind so I could up the compression ratio to 10:1 and have more low end torque to boot. It was still more peppy than the Mazda and the VW Golf diesel. The AFR gauge made it easier to jet to get the AFR to where I wanted it. The fully adjustable distributor let me advance the timing to as much as possible at every load/RPM combo. It was great fun to experiment. I felt like I was doing the exact opposite every other air-cooled VW owner would do. I had increased the compression ratio, advanced the timing and made it run much leaner. Yet the results were fantastic, a solid 30mpg combined and the thing was very peppy. The downside is that the temp gauges, oil and heads, indicated that the engine actually ran cooler, too cool actually. Apparently 16:1 AFR's actually run cooler than 14.5:1. I had also ceramic coated the exhaust ports, which now I see was not necessary.

Now I have a Toyota hybrid. It's practical and reliable. But other than that, it's about the most boring car I've ever owned. I do all the maintenance I can to it. I can't, for the life of me, figure out how to properly flush the brake fluid, so that's one thing I take it to a mechanic to work on. The infotainment center also no longer works, and I'm not going to pay anyone to fix it since I know it's going to be at least $300 and will probably go back out again (it's been fixed once already).

[Ecky]

Driver mod - slow down. Losing 10mph will do more than any (or every) other mod you can do to a car. On the highway, anyway.

Otherwise, it's between tire pressure and grille block, and I think I lean toward tire pressure. I like the sharp steering that comes with it, and I think it pays higher dividends throughout the year, even if a grille block is tremendous in winter.

[freebeard]

Originally Posted by Isaac Zachary

The AFR gauge I put on the 1972 VW Super Beetle helped me keep my foot into it just before the enrichment circuit would activate.

Was there a thread on this? I recall you posting while you were driving this.

Asking for a friend....


Putting 165-50s on the front hasn't worked out as well; possibly because I didn't fit matching rears.

[Nissandriver]

Tires are one of the easiest mods. I went from 185/60/14 to 185/75/14 on my 94 Sentra. I'd guess my mileage has been about 5 mpg better. The first year on the original size tires was 35 mpg. With the tire change my mileage calculations remained the same 35 mpg but the taller tire requires a correction factor. I divide my speed or mileage by 0.93 since I covered 100 miles on the interstate many times while only recording 92.4 miles on the odometer. The only time I've gotten worse than 40 mpg since 2020 was two long trips on the interstate at 80 mph with the air conditioner running most of the time.

[freebeard]

I once had a police officer try to convince me that putting bigger tires on my car would make the speedometer read low. I countered that the speedometer is fed but the left front wheel, and the rear tires were stock and the front undersized. ....and I knew the correction factor.

OTOH, I had a mechanic say 'that's fast what did you do to it.' I explained that it wasn't.

[y2kbug]

Thanks to all those who responded!

Originally Posted by freebeard

The ultimate mod is a boat tail; but they're a pain in the.... parking space.

I use my trunk in my car everyday for work, unfortunately i believe that may be more trouble than its worth on the corolla. I'd like to try that one day, once i can live in a place with enough room to have more fun projects.

Originally Posted by Isaac Zachary

For fuel mileage? It was buy a 1985 VW diesel and keep the RPMs low and floor it for a "pulse and glide" technique. I'd get over 50mpg on the highways. One trip I did just about 600 miles but couldn't get more than 10 gallons into the tank. The car was also immortal. 3,000 mile oil changes and it just wouldn't die even after who knows how many miles. It had at least 300,000 miles on it, but the odometer was broken and I drove it for 7 years. The next car I got I did 30,000 miles that year, and I assume I drove about the same in that Golf, so 7 x 30,000 = 210,000 + the at least 300,000 miles meant it had over 500,000 miles on it. And that's the lowest guess, it probably had a lot more on it.

Advancing the timing on my 1993 Mazda 323 also was a big help. That, and again, stick shift that I keep the RPM's as low as possible, but in a gasser you keep it mostly floored, but not all the way. The AFR gauge I put on the 1972 VW Super Beetle helped me keep my foot into it just before the enrichment circuit would activate. In all of these cars I'd usually be in top gear at around 25mph. The Mazda got around 45mpg on the highway.

The 1972 VW Super Beetle was the most fun, even though it got the worst fuel mileage. I got a custom cam grind so I could up the compression ratio to 10:1 and have more low end torque to boot. It was still more peppy than the Mazda and the VW Golf diesel. The AFR gauge made it easier to jet to get the AFR to where I wanted it. The fully adjustable distributor let me advance the timing to as much as possible at every load/RPM combo. It was great fun to experiment. I felt like I was doing the exact opposite every other air-cooled VW owner would do. I had increased the compression ratio, advanced the timing and made it run much leaner. Yet the results were fantastic, a solid 30mpg combined and the thing was very peppy. The downside is that the temp gauges, oil and heads, indicated that the engine actually ran cooler, too cool actually. Apparently 16:1 AFR's actually run cooler than 14.5:1. I had also ceramic coated the exhaust ports, which now I see was not necessary.
(it's been fixed once already).

A majority of car people i've talked to have something good to say about either vw bugs or diesel vws. I don't think there is much adjusting i can do on my vehicles engines, i can only keep it maintained and hope the computer works in my favor.

Originally Posted by Ecky

Driver mod - slow down. Losing 10mph will do more than any (or every) other mod you can do to a car. On the highway, anyway.

Otherwise, it's between tire pressure and grille block, and I think I lean toward tire pressure. I like the sharp steering that comes with it, and I think it pays higher dividends throughout the year, even if a grille block is tremendous in winter.

Ive had great luck by slowing down. 22-23 driving 50-55 mph or 18.X driving 73 mph in my dodge is a big difference to me. I run the tires a few lbs over the recommended pressures maybe i should try max pressure and see if i makes any difference. Grill block never crossed my mind until i got on this website. I'd like to try that out, especially in the winter.

Originally Posted by Nissandriver

Tires are one of the easiest mods. I went from 185/60/14 to 185/75/14 on my 94 Sentra. I'd guess my mileage has been about 5 mpg better. The first year on the original size tires was 35 mpg. With the tire change my mileage calculations remained the same 35 mpg but the taller tire requires a correction factor. I divide my speed or mileage by 0.93 since I covered 100 miles on the interstate many times while only recording 92.4 miles on the odometer. The only time I've gotten worse than 40 mpg since 2020 was two long trips on the interstate at 80 mph with the air conditioner running most of the time.

I have been thinking of getting 2 larger tires for my car but i'm not too thrilled over the speedometer being inaccurate. I guess its not that bad because i calculate out the error to still get accurate numbers.
do worn out tires get better mpg than new tires?

[redpoint5]

Originally Posted by freebeard

I once had a police officer try to convince me that putting bigger tires on my car would make the speedometer read low.

I had an officer admit that he was doing 130 and loosing ground to me. My comment was that it sounded dangerous to drive so fast.

[freebeard]

do worn out tires get better mpg than new tires?

Worn in, not worn out.

Once you know the conversion factor for your speedometer, just add some tape or paint marks.