Engine Performance Vs Mileage....

[2007_Crown_Vic]

Hi everyone,

I have been looking for a 1987-1993 5.0 GT for a while and finally have a few lined up that I think will work out. The one I am really interested in is bone stock other than a K&N filter, advanced timing and a Flowmaster exhaust. The other has E303 cam Edelbrock Performer Intake, and Aluminum trick flow heads (possibly more that isn't listed, I have heard depending on how far you go with upgrades you have to upgrade your injectors and MAF and stuff).

I have never cared about gas mileage for performance/fun cars before but I am planing to use it as a daily driver for the summer months so for once gas mileage is somewhat of a concern. Luckily for me my total drive time per day is usually around 30-40 minutes so I don't need a car that is great on gas mileage, I just don't want to end up stopping at the gas station daily either.

My question for the experts here is, does anyone know what impact the above modifications would have on gas mileage? The manufacturer mileage said the car should get about 18MPG city and 23 MPG highway. Using that as a baseline however true it is or isn't, should I expect something like 16MPG/21MPG or something more drastic like 8MPG/13MPG (likely a huge exaggeration.... hopefully, lol). I have heard in some cases timing and a few intake/exhaust mods can actually increase mileage but I doubt this is one of those cases.

Thanks for any tips or information you may have.

Adam.

 

[Mustang5L5]

Get ready to hear claims of anywhere from 8mpg to 35mpg.


For the most part, certain mods should increase gas mileage, but they often contradict other kids done in the name of speed. Most guys here use their mustangs and weekend cars, and don't really care for mpg.

My car? I prob could get decent gas mileage, but for the most part I stop at the gas station to top off each time I drive.

A bone stock 5.0 wity 2.73's...I could see that hitting mid 20s on the highway


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[stykthyn]

My gt40 set up gets around 16 in town and my best hwy trip was about 25mpg. Erring on the side of caution and your right foot expect 13 city and be grateful for anything else.

 

[Omega]

Depends on how you drive it. In my old carb'd cars I'd average about 12-13 in town getting on it a bit. Maybe 20 on the highway @ 70. The best I've ever gotten was ~30 @ 100 MPH (3.08 gear with SROD trans).

For what it's worth, I am able to wring some ridiculous MPG's out of cars. Like my DD... 4500lbs. with a 5.5 v8.

 

[stykthyn]

The amg comparison I don't think applies here. You're talking dinosaur efi to modern engineering. Let's pit a race between the wright flyer and an f15. They both fly so it must be a valid point.

 

[2007_Crown_Vic]

Thanks, that all sounds good. I am still hoping that everything works out and I can get the stock, original car. I just wanted to make sure that some relatively minor modifications were not going to make the mileage so bad to where it wouldn't be a car I could drive everyday. The 2007 Crown Victoria I drive now isn't exactly great on gas and it seems like either the stock version or a slightly modified version of these Mustangs won't be much different. Controlling my foot might be a little more difficult with the Mustang than the Crown Vic, but that will be my fault not the car's, lol.

 

[stykthyn]

You get used to it. I would think that a crown vic would be a decent comparison

 

[2007_Crown_Vic]

Yeah, if the numbers I looked up are right, it is about 1000LBS less than the Crown Vic so I am looking forward to that. I have also made do with automatics for so long I am really looking forward to getting back into a standard. I still like my old 350/4 speed, but 5 speeds are fun too.

 

[a91what]

You would be amazed how much a good tune can affect mpg...

(I tune My own car with an aftermarket ecu)

I have seen as much as 23mpg with my e303 cam and 3.73 gears this is combined milage..... but mine is far from "normal"

And if I can keep my foot out of it.

 

[2007_Crown_Vic]

That is good to know. The plan was just to drive it as is for a while, but one of the things that draws me to these cars is the amount of aftermarket parts and kits available for them. Once I am no longer interested in using it daily, there are so many kits and modifications I can do to make it more of a weekend car where gas mileage isn't really a concern. Even with just the limited research I have done over the last few days I really like the top end kits that come with everything you need to easily add as much power as you like. My weak point will for sure be programming/tuning. I am used to much older cars to just have for fun and tuning with computers isn't something I have done before. I would like to learn because I hear shops charge a fair amount to do it.

 

[Omega]

The amg comparison I don't think applies here. You're talking dinosaur efi to modern engineering. Let's pit a race between the wright flyer and an f15. They both fly so it must be a valid point.

To an extent you're right, however, it's HOW you drive that makes the mileage. When I did that, I was specifically TRYING to get the best mileage I could out of the car. But you can do it with any car.
I had a 2nd Gen probe GT that I managed to get about 32MPG AVERAGE, 50/50 city and highway driving. The car's rated 20/26.Even in a Mustang, you can get exceptionally good mileage if 1. you keep your foot out of it (haha... yeah right), and 2. find its sweet spot. Every car has it. A certain speed/rpm that's it's just incredibly efficient.

For a 302 to be efficient, you can't let it spin fast.

 

[Mustang5L5]

130 mile ride home today in the DD taurus. 3.5L, 4400 lb car and loaded with family crap and running the AC the whole time. Averaged 30.2 mpg on 87 octane.

I think ford is really hitting their stride now with fuel economy numbers due to cafe, but i doubt I'd see the same numbers out of my 30 year old dinosaur efi setup unless I really tried very hard. Like 2.73s and babying that gas pedal. Even then I think 30 mpg out of a 5.0 is a stretch.


I used to see 25-26 mpg out of my 2003 GT, but again. Long highway stretches and reaaaaaaally babying that throttle. Almost boring driving really.


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[2007_Crown_Vic]

Well, I guess I will find out for myself soon. We ended up buying the 1990 GT that we went to look at. It was simply too good to pass up. It is by far the nicest, cleanest one we have found. On top of that, he had history all the way back to the original owner (he was the third) and he even kept a log book about where the car went, service work, things he had done to it, etc. The bottom of the car looks brand new, the carpet and interior looks brand new, even the CV boots and ball joints/bushings look brand new - it really is amazing. Here are some pics:

 

[stykthyn]

Clean. I would have pounced on that too

 

[a91what]

That's an amazing find it'll almost be too hard to mod it

 

[2007_Crown_Vic]

Exactly! That's what we were thinking on the way home. Our goal now is to try and maintain it to the standard that the last owners have. I couldn't bring myself to start taking off cylinder heads or anything like that on a car that is all original, so clean and well cared for.

If we want a fox body to modify and have fun tuning on I guess we will just have to buy another one that isn't so original, lol.

 

[Mustang5L5]

That's a clean car.


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[Omega]

130 mile ride home today in the DD taurus. 3.5L, 4400 lb car and loaded with family crap and running the AC the whole time. Averaged 30.2 mpg on 87 octane.

I think ford is really hitting their stride now with fuel economy numbers due to cafe, but i doubt I'd see the same numbers out of my 30 year old dinosaur efi setup unless I really tried very hard. Like 2.73s and babying that gas pedal. Even then I think 30 mpg out of a 5.0 is a stretch.


I used to see 25-26 mpg out of my 2003 GT, but again. Long highway stretches and reaaaaaaally babying that throttle. Almost boring driving really.


Sent from my big ass iPhone 6 using Tapatalk

It's doable out of a mildly built 79-82 (they're lighter) with a 3.08 and an SROD which has a .50 OD. At 100 it was @ 2000RPM. Just barely turning. 600 Vacuum secondary tuned just right for the combo. Built as a torque motor mainly. Pulled like crazy to 5500 RPM then fell flat on its face.

 

[2007_Crown_Vic]

Hi Omega,
After driving mine around for a few days getting used to it, to me it feels like around 1800RPM is likely where it would be getting its best mileage so it is interesting that you mentioned 2000RPM above. Does everyone seem to agree that this is about where you best mileage for cruising speeds would be on a stock version? On the way home when I first got the car I was doing roughly 100KM/h and was trying out 4th gear vs. 5th gear - 5th put it around 1400-1600RPM which felt and sounded like it was just chugging along where 4th put it around that 2000RPM. It sounded and felt better in 4th but I wasn't sure if the lower RPM with a higher fuel mixture was more beneficial than the slightly higher RPM with a higher air mixture... either way, this car is a lot of fun so far. Its ridiculous how easy the wheels spin when you get on it in first gear.....

 

[great white]

...even the CV boots.... look brand new...]

Umm.......