30mpg no matter how its driven

[straight5]

I've been wondering about my car. It seems that no matter how it's driven, it gets right at 30mpg. Volvo 850 5speed
I can drive it really easy on a road trip, or I can drive it around town like I stole it, and I still get the same results.
Premium fuel or regular fuel doesn't change anything either.

This is not an effort to disprove anything else on this forum -

In my other car it makes a difference by several mpg depending on how it is driven. That takes the driver out of the equation
It has always passed emmisions testing (pre- obd2 sniff test) way under the limits.
Any ideas why it doesn't get better mileage when driven easy or on road trips?

[ShadeTreeMech]

I would suspect something about the transmission. If its a tranny with a low overdrive, you won't be able to get over a certain amount from the engine having to spin too fast on the highway. Highway speeds could be affected by the generally boxy shape of most volvos I've seen too.

[straight5]

IIRC it runs 2050rpm at 55mph and yea thats kinda high compared to newer cars, but I can run 55 with a very light foot, or run NOTICEABLY faster - same results
93 volvo 850, 5speed, stock, sounds good, slow- y - Car Videos on StreetFire

[Ladogaboy]

My old Ford F350 (1974) was seemingly the same way. Three-speed automatic with a 4.11 rear diff, it never seemed to get better than 11 mpg no matter how it was driven either. Unless you count the one time that I hypermiled (unbeknownst to me at the time) it. I was able to go somewhere close to 20 miles on one gallon of gas (albeit under ideal conditions).

[Big Dave]

I hear that a lot from guys with pickups, albeit at a much lower MPG level.

My answer: you're overgeared.

The closer to "properly geared" (for max MPG) the more sensitive the vehicle is to how it is driven. You're probably leaving a lot of MPG on the table, geared as you are.

[straight5]

Fairly soon, this car should become a third car for the wife and me. I've been considering making it a toy. It has the 5 cylinder 2.4 liter 20 valve engine.

It could be a high horsepower sleeper, or possibly a high MPG daily driver. Either way, it will require a lot of mechanical work - I do all my own mechanic work.

I don't want to do a lot of work to the car to try to get high MPG, and in the end still just get 30mpg.

[ShadeTreeMech]

Assuming you have lower that optimum gears, it's fairly certain changing to higher gear ratios will improve mileage drastically.

[straight5]

correction
3100rpm @ 80mph
2700 @ 70mph
2300 @ 60mph
1900 @ 50mph
redline is 6200,
2.4 liter, 5 cylinder, twin cam, 20 valve.
over geared? When my wife drives it, she complains that it doesn't have any power - but she expects the power in the lower RPM, and being naturally aspirated, it makes the best power between 4k & 6k rpm.
I'm just not sure how well it would pull it's self if it was geared much higher.

[Ecky]

Originally Posted by straight5

over geared? When my wife drives it, she complains that it doesn't have any power - but she expects the power in the lower RPM, and being naturally aspirated, it makes the best power between 4k & 6k rpm.
I'm just not sure how well it would pull it's self if it was geared much higher.

It's not a crime to downshift to pass. One possibility is to just swap out the top gear.

[beatr911]

Try documenting each and every tank with notes and post them to this site to see a graphical representation. Nobody gets a straight 30 mpg every time. I suspect you'll begin to see some trends that you can then exploit to your favor. If you can also have your wife document when she fills, she will be more aware and might change her driving habits for the better as well.

Not that it's necessarily the case with your experience but I've noticed something about variable driving habits or the difference between drivers. Possibly it could explain at least some of the non-variability you or others are seeing.

If I drive the entire tank with good technique and only have a very occasional outburst of speeding fun (like once or twice) the tank mileage doesn't suffer. If I drive like an idiot the entire tank and hypermile for say only a single commute, I'll get idiot mileage. The moral is the tank mileage is the average of the driving technique used over the entire tank and small variations don't affect mileage much itether good or bad. For your driving 30 mpg is it. Wayne Gerdes would probably be able to squeak 37mpg out of it but he can drive on the extreme edge of hypermiling.

I use this to my advantage. Hypermile 95% and have some fun for the 5% or so. I still think driving is fun and don't want to make it all about maximum mpg.

The other comments are probably spot on about gearing and aerodynamics. It could very well be that the mpg of the high drag body at speed equals the city mileage. Maybe the car needs some repair in order for it to reach it's potential.

In the '80s I had a Kawasaki GPz 550 that always seemed to get 60 mpg. Gentle all city driving or backroad strafing at WOT and 100% braking. Didn't seem to matter. Tank after tank. Looking back I didn't know about hypermiling and probably could have done better in some modes of driving. I also didn't document it, just figured it in my head at the pump. I suspect the figuring in the head was the bigger problem.