Fuel Economy Question

Topic: Fuel Economy Question (Read 3092 times) previous topic - next topic

Fuel Economy Question

October 31, 2004, 02:28:51 AM

What kind of MPG is everyone getting? I'd prefer that the numbers refer to stock injection systems. The reason I ask is that I may upgrade to an SEFI 5.0. I currently have a 3.8 CFI. I was just wondering if the numbers are about the same for each. As of right now, I get about 18 MPG mixed driving.

Re: Fuel Economy Question

Reply #1 – October 31, 2004, 02:35:44 AM

http://www.fueleconomy.gov will give you the manufacturer's numbers for both, for a starting reference.

As for personal experience, I don't have exact numbers because I haven't been precise about it yet.. writing stuff down, etc. But I'd say the manufacturer's highway numbers are probably pretty close to correct on my 3.8 CFI. I'll have to get back to ya on the 5.0 SEFI.. heh.

Re: Fuel Economy Question

Reply #2 – October 31, 2004, 03:29:54 AM

My '85 CFI 5.0 gets about 19-23.

Re: Fuel Economy Question

Reply #3 – October 31, 2004, 07:25:30 AM

My 88 5.0 SEFI gets about 27-28 on the highway (thanks to its 2.73 rear gear it idles along at 1500 RPM at 70MPH) and about 15-17 city.

Re: Fuel Economy Question

Reply #4 – October 31, 2004, 07:31:51 AM

18ish when im an ass, 27ish when im a good driver, 3.8L CFI

Re: Fuel Economy Question

Reply #5 – October 31, 2004, 12:50:58 PM

Quote from: Bird351

http://www.fueleconomy.gov will give you the manufacturer's numbers for both, for a starting reference.

As for personal experience, I don't have exact numbers because I haven't been precise about it yet.. writing stuff down, etc. But I'd say the manufacturer's highway numbers are probably pretty close to correct on my 3.8 CFI. I'll have to get back to ya on the 5.0 SEFI.. heh.

According to that link, the 87 v6's got worse mileage on the highway and only 1 better in the city when compared to the v8. Why would anyone have purchased a v6?

Re: Fuel Economy Question

Reply #6 – October 31, 2004, 01:37:32 PM

Never claimed it made sense.. just that it seemed about right for my car. :p

Re: Fuel Economy Question

Reply #7 – October 31, 2004, 09:26:05 PM

Quote from: amooset

According to that link, the 87 v6's got worse mileage on the highway and only 1 better in the city when compared to the v8. Why would anyone have purchased a v6?

The reason the 8 got better mileage on the highway was because it idles along at highway speeds, while the 6 needs to be given more throttle to acquire and maintain higher speeds. Also, the V6 has a shorter rear gear (usually 3.27 compared to the 5.0's 2.73 or 3.08).

I witnessed the same thing with my Cherokees. I had an old '87 Cherokee with a 2.5 4-cylinder SEFI and automatic. The thing got about 10 MPG highway because it was very underpowered. You had to be at wide open throttle just to maintain 65 MPH (70 was unattainable). The current '87 I have now is essentially identical (auto trans, 4X4, no a/c) except that it has the 4.0. It gets about 20 MPG, seemingly regardless of city or highway. I'm guessing that's because it's an aerodynamic travesty, but even still, it burns half the fuel the old 2.5 did. I think the 4-cyl version probably had 4.11 gears while the six has 3.73's, too.

So why does anybody buy the smaller engine? Because the smaller engine models are cheaper to buy and insure. A V6 LX cost thousands less than a very comparably equipped 5.0 LX. Combine that with the fact there was only a 10-hp difference between the two engines and people had a hard time justifying those thousands (though the 5.0 is certainly torquier)

Re: Fuel Economy Question

Reply #8 – October 31, 2004, 10:22:37 PM

i get about 29-31 on the highway, but about 9 in the city

cant figure out why. ever sence i put on duals with no cats, my mielage went from about 17 to 9 mpg city

guess i dont have enough backpressure. but the hp sure went up

Re: Fuel Economy Question

Reply #9 – November 01, 2004, 01:19:08 AM

my friend's 5.0 generally gets 17-19 mpg city.

Re: Fuel Economy Question

Reply #10 – November 03, 2004, 06:27:28 PM

Maybe It's just me but My 88 5.0 xr-7 gets 14-17mpg in town and 20-22mpg on the highway any my cougar purs(thanks to castrol full synthetic). I can barely notice the engine is on at times. I do know my digidash tells me my car drinks gas. Any Ideas as to why. Everything is stpen 15. 114,000 miles. (exhasust has some rust too) could my digidash be wrong? bad oxygen sensors maybe?

Re: Fuel Economy Question

Reply #11 – November 04, 2004, 10:16:11 PM

with my setup I get ~10-12 mpg city and ~29mpg all highway.

Mixed (commute from work and back) I get about 20-23mpg.

Re: Fuel Economy Question

Reply #12 – November 06, 2004, 06:01:03 PM

I get 15 city and 23 highway with the efi v6 and 3.73's out back