Highest MPG V8?
 

I know that the V8s are generally not known for their fuel economy, but I though I remembered that the Corvettes were rated about 32 MPG highway. I couldn't confirm this, though, since the Chevrolet website only claims 26 MPG highway (still not a bad number).

I also saw the recent article on the Oldsmobile that got good mileage, I think it was about 19 MPG highway.

What other "high" MPG V8s exist?

Anyone (besides myself) have any gas-saving V8 projects in the works?

-Bob C.

even the ol 350 carbed boats of the past got very high teens to mid 20's highways...

we had a Chevy caprice that would get about 19-22 mpg on highway if you drove it right...

The Corvette constantly gets mentioned on fuel economy top 20 lists and such.

The Ford Crown Victoria platform 23 freeway on the new rating system. Mustang GT gets 22-23. From personal experience the Crown Vic actually gets closer to 26-28mpg on a constant freeway cruise tho.

Lexus GS 460 gets 24 freeway on the 4.6L V8 as do most of their other V8 cars.

Cadillac STS with 4.6L gets 24 and the Infiniti M45 gets 21

There aren't a whole heck of a lot of V8 cars out there anymore as most companies have gone to 6 cylinder engines. Regardless of that fact though, having V8 cars that are getting int he 20's on the new testing the EPA does is pretty good.

'97 Expedition, SOHC 4.6 with a towing package ... 22 mpg actual at 65 mph.

I'm sure with some aerodynamic mods that could be taken to 25 mpg and maybe even higher.

Virtual boattail anyone?

95 Mustang 5.0 , 27 mpg actual at 70 mph cruise..

Check out my "88 Mustang (https://www.gassavers.org/garage/view/1408). With the 5.0 liter V8, 5-speed and 2:73 gearing, I am getting close to 30 mpg regularly on my commute. The torquey V8, manual transmission and high gearing combine for good economy if you drive carefully. The newer cars with more efficient electronics than my 20 year old car should do better.

I've heard of crown vics pushing into the 30s on the highway, that might have been with some mods though.

I should have probably said, that's about an 85mph highway cruise. At 65-70 we actually got around 31-32.

I can get around 25-26 mpg out of my '83 Eldorado with the 4.1 liter engine. On one trip I did get about 32 mpg with a lot of drafting...

The Vette and Camaro both, with the LS/1 V8 had that massive .5:1 6th gear which took revs down to ~1400 @ 65. While they were never actually rated at 32mpg, many owners of both cars have touched 30+ and most can consistently and easily pull better than 27.

LT/1-equipped cars like the Cadillac Fleetwood and Chevy Impala SS, among others, were capable of mid-20's, not bad for a 4000lb+ V8 car. Similarly, the Cadillacs with Northstar V8's are known for getting ~27mpg on the open road with little effort.

Some folks have swapped EFI onto their vintage Mustang small blocks and together with a 5-speed manual swap get 25+, some even claim 30 highway.

My best was 22mpg in my '68 Mustang. It had a 302 and no overdrive, but it had the tallish 2.73:1 rear end and the hardtop body was the lightest bodystyle weighing in at ~2750lbs. I got that on the flats of the Central Valley, CA, doing about 60 on Interstate 5 with freshly aired up tires. It was a bit of a freak tank, I usually got 18-19mpg at that speed. May have been the Flying J pump I got gas at...

I've heard 34 from a C5 z06 owner. Don't know the particulars of it. I know that they have a lean burn system in the PCM. I'm sure with hptuners more could be squeezed out of it.

My dad swore that he could get 25 mpg with his '66 Dodge Polara, 318 V-8, two barrel carb. But I never personally verified that.

My dad owns an '03 Corvette, so I know for a fact that they can get 30+ mpg if you drive it easy. The RPM's are so low while cruising. I think at 55mph it only turns something like 1500, but tons of power on demand, if/when you need it. ;)

Yeah. I've always heard a lot of good about the FE that LS1 could get

I knew there was a good reason to drop a Northstar in my minivan.... :D

Having the RPM so low just astounds me. You still need some power to move the car, but I guess if you have so little aerodynamic resistance the engine doesn't have to produce much torque, so it's okay to run it "down in the mud". I'd be curious to know what kind of timing numbers they use under load at 1500 RPM, since the piston speed is so slow.

I guess a lockup converter is also helpful with the automatics (crown vic & northstar), of course the 5-speed manual (i.e. mustang) being the odds-on favorite.

-Bob C.

I've heard lots of claims like that also, but they also sounded like "wives tales" to me too...

-Bob C.

It's not that shocking that a Vette can do 55 mph at 1500 rpm, when you consider that a VX is only turning 1852 rpm at that speed. 1.5 liters.

https://www.fuelly.com/attachments/fo...cc63cc85f5.jpg

If you look at the torque on that engine (2001 Corvette test results) you'll see why the engine is able to turn so low.

Obscene amounts of torque everywhere. Over 300Ft-Lbs as low as 1500 rpm!

It's also why this car can cost only 65K and not only keep up but in a lot of cases beat 200K+ sports cars in performance, feel and fuel economy. This is actually the only car GM makes I would buy.

The mpg numbers in the Vette are not strictly because of a fuel efficient engine. It's a combo of the gearing and the aerodynamics of that thing.

I've heard there's a 10 mpg difference between the A4 and M6 vette.

Oooh, that kind of bothers me. As far as performance and fuel economy goes, the Corvette holds it's own, but this is due to a complete lack of luxury, for the price it's a heck of a deal, but in no way does it feel like a ferrari, sl55, 911, or any other non-domesticish car. They just don't have the solid, quality, and fine materials. But if all you want is a little sporty tin/plastic can, they can't be beat.

/Rant

Back on topic, I've also got a V-8 and am trying to see how good of gasmileage I can get with it. I have finally got my o2 sensor working and I can't wait to see what kind of numbers I get on my next tank. I should be able to do pretty good with a drag co. of .37 (not good, but for '85 it's pretty good) and the "economy" version. 3.8 liters

I would think the Olds Aurora would be up there with the smaller V8.

regards
gary

I agree the Oldsmobile Auroras were also pretty decent. Here's one driver claiming to get 29.3mpg out of theirs. https://www.fueleconomy.gov/mpg/MPG.d...rue&details=on
GM knowing their target market and thinking upside down as usual put lots of its R&D into making the v8s more efficient instead of making efficient engines more powerful like other car makers did.

seems to alway be the word " highway" behind any MPG numbers mentioned on new car ads.

1985 Chrysler 5th Avenue, 318 2bbl, lockup torque converter, 205/15 tires. All the stuff out of the trunk, tires pumped up to 40psi, windows up no air on (hot inside but worth it!!). Cruise control @ 55mph on I80 relatively flat. I could get 30mpg. Not bad. I was pretty happy.

1967 Plymouth Barracuda, 318 4bbl, lockup torque converter (newer 904), no junk in the trunk, 60mph, 3.00 rear ratio. I could get 25 mpg. Had 245/14 tires, not the best. The motor had stuff done to it, but probably helped out it's mpg. Same highway drive as the above 5th ave.

The 1955 Moto Guzzi 500cc V8 Grand Prix motorcycle engine..

The liquid cooled engine only weighed 45 Kg, put out 72 hp and would reach 172 mph in the Guzzi GP racer.. A speed that was not equaled until thirty years later.

https://upload.wikimedia.org/wikipedi...seoV8-1957.JPG

https://www.webbikeworld.com/Moto-Guz...s/guzzi-v8.jpg

1988 Ford Thunderbird, too, same engine.
Thou to get 27 I had to keep it around 62-63 cruise controlled...
Or was it 29? It's been so long lol, but thereabouts, assume 27 to be safe.
I suspect possibly the Mercury Cougar and the Lincoln Continental Mark VII (or 8?) of about or around those years as well.

My '92 9C1 Caprice regularly got 22MPG mixed and could pull 24MPG highway. It was a TBI 5.7, but the bodies on the '92 and up we amazingly aerodynamic, I could coast forever and ever and it took very little throttle to accel from 65-85. I wasn't hypermiling back then either, I wish I still had it to see what I could get now. My truck as the same engine but MUCH worse aero :p.

My last car was an '04 GTO with the LS1 V8 and a six speed. It would regularly get 27-28 mpg highway, but it was geared a little different than the 'Vettes and F-bodies with the LS1. What a fun car. :D Unfortunately it was too much fun.

I used to regularly approach 30 MPG in my old 74 Chevy C-10

300,000 miles, a/c, cruise, 350 V8, 4bbl carb, TH350 automatic tranny.

FE mods:

Electronic ignition out of a 75 Chevy van, platinum plugs, flipped air cleaner lid upside down, and aftermarket cruise installed.

Then in 75 they started putting emissions crap on light duty trucks and FE dropped quickly.

-Jay

Bull ****

https://www.elisemods.com/images/c6vette.jpg
https://www.autoweek.com/apps/pbcs.dl...73244466514443

End of thread.

I'm sorry if you don't believe it, but I did do it. Emissions stuff really takes its toll on FE, especially the early emissions stuff. In the 74 Chevy I'd do 27 - 28 on the highway, and I'd usually average 20 in daily driving. The older cars got pretty decent mileage. Even my old 1980 Bonneville wagon regularly got 16 MPG with a 4bbl carb, TH350 tranny,a big block V-8, and a 16 year old driving it. When I bought Rusty I thought Wow, this truck has dual tanks. Imagine how far I can go on dual tanks... Turned out that it needed dual tanks to go as far as the 74 went on one...

In addition to emissions, there's the sheer amount of power available in newer vehicles, required for these purposes:
- decent acceleration with the much larger amount of weight in modern vehicles
- 2wd regular cab 1970 C10: 3,737 pounds of heavy iron
- 2wd regular cab 2008 Silverado: 4,453 pounds of thin sheet metal, hollow aluminum driveshaft, and hydroformed frame
- additional performance for consumers with higher standards
- additional other parasitic loads

Also, consider that modern emissions stuff, while more numerous, is less parasitic. For example, modern catalytic converters flow well...old ones, not so much.

Now, on the weight issue, at least with trucks the extra weight comes with extra capacity, so maybe you could compare a modern 1500 to a classic C20...

Tell you what, they get a Kia Rio5 with the 3.5L V6 with a 5-speed and RWD. Buy that puppy in seconds. Probably get pretty decent mileage too.

1978 Olds 88 diesel, until the engine blew up. Regularly went 750 miles on a tank.

regsards
gary

If my memory of late 70's GM cars serves me correctly that car came with a 25 gallon tank? My grandfather had pretty much the same car (84 Delta 88 Brougham). Dad & I were fighting each other for who would get to have grandpa's Delta when he was ready for a new one, but then he just traded it in... :(

Anyway, back on track here... for a 20 gallon fillup on your Delta 88 would mean you got 37.5 MPG. Not too shabby. Even 750 miles over 25 gallons is 30 MPG. All I have to say about that is WoW!

55 speed limits helped.

Jay it was my brothers car, long ago memories, the motor disintegrated at 40k miles, probably 700 per tank, or a larger tank, but it did get better than 30 MPG.

This was the huge square land yatch.

regards
gary

I see, it must have had one of those gasoline 350's that GM hurriedly attempted to convert to diesel - I don't think any of them lasted long.

-Jay

The Mercury Grand Marquis that my dad has will get about 27-28 highway running 65-75 mph. It has the 4.6L with O/D transmission. Of course it is nothing other than a dressed up Crown Victoria. I'd like to take it on a longer highway drive just to see what I could get out of it. I think I could easily break 30 mpg.

Edit: It will get about 24-25 mpg in just normal shorter trip driving, trips of 50 miles or less driving 50-60 mph.