Most Efficient Speed

[pitzel]

Ok, I recently inherited a 1992 Cutlass Supreme from my deceased grandfather as part of his estate. Petrol is very expensive here in Canada, so I would like to drive at the most efficient speed for long drives.

 

When I received the car, it was getting approximately 20-23USmpg on the highway doing roughly 105 km/hr. A new oxygen sensor brought that number up to 29mpg, albeit at speeds of 110-120km/hr.

 

Due to failure of some vacuum lines, the autothrottle was inop., and I managed to diagnose and repair said lines. With the autothrottle, I can select a speed and leave it there, returning to the back seat for a snooze while the car takes me to my destination.

 

All said, what is the most efficient speed to drive this car at? 90km/hr? 100km/hr? 110km/hr? Surely I should be able to achieve into the low 30 USmpg range on the highway at the car's optimum speed -- EPA ratings tend to be very conservative I have found (my mother's 1990 3800-engined car gets better than 30 USmpg)

[digitaloutsider]

On the highway, I get my best gas milage at 85-90 MPH :shock: :shock:

[pitzel]

I forgot to add, 3.1L V6 engine, 4-speed automatic transmission (4T60-E), tyres pumped up to 38-40psi.

[supreme_style21]

Wow.. You win the award for 'Most Canadian Words in One Post'

 

I find mine to run the best at 62 mph. No idea what that is in your speed. Slightly different engine, but should result in similar numbers.

 

edit: I dunno if the tires are to be run so high? Mine are always at 34 max.

[GutlessSupreme]

around town I find the best speed is just above 40 MPH, right at the bottom of fourth gear. On the highway.. I get pretty good mileage at most any speed. I dunno Maybe 75ish MPH.

 

PS - sidewalls on my tires say about 35 PSI. I don't know what the door sticker says.

[Justin]

If you're looking for the best mileage (kilometerage?) I'd say pump your tires to at least 35, and drive about 85 kilos, just enough for your trans to be in the highest gear at a low rpm.

[THe_DeTAiL3R]

With my 2.8, I get best gas mileage going about 50-60mph (80-100km/h). That puts it in overdrive and is at 2000-2500RPM. Gets me in the low 30mpg range (average).

 

As far as tires, 2 of mine say 40psi max, the other 2 say 35 I think, but I have pumped them up to 40 before, last time I did 35 just cause I think 40 is too much and it was also morning (colder outside).

[Guest Gp crazy]

i just went to six flags and avg. was 27 on the way out & on the way back i got more on the dic it read 32.4 and 398-402 miles to a tank at 85 which on my speedo = 110 mph I still do not know why? But 90 = 64 mph ? any ideas? the tire size is right 215-60-16 also at 85 the tach was 2900 or so. i just leave it alone because i know where my normal speeds are. jeff b

[SigEpCutlass]

i usually get my best gas mileage doing about 65-75mph. I never drive below 65mph on the highways....

[supreme_style21]

i usually get my best gas mileage doing about 65-75mph. I never drive below 65mph on the highways....

 

I used to be that way until I got raped.. now I can't afford to get caught speeding or I'm close to dead. I usually got 25 mpg around 75 mph. Now that I've gotten used to keeping it at 60, my gas mileage went up to around 34.

[GPRACER]

I'm with ya on those high gas prices, I'm paying almost 1.00/litre here. As for mileage, I find my car best at aprox 125-130 kph. The police don't like it too much though, I got off witha warning last week for doing 134 in a 100 zone. Stick with the tire pressure thats on the door, Mine is 30 psi. When you are at highway speeds the air in the tires heat and expand to about 38-40 anyways. If you start with 40 chances are you will have abnormal tire wear which will eat up your meagre fuel savings pretty quick. Just going by experience here I drive 1000+ kms a week all highway.

[93CutlassSupreme]

38-40 is too much

 

my sidewalls say 35 max, at 35 psi my car rides like total shit

 

30 works for me

[94CutlassSLCoupe]

i remember getting 32mpg @ 70-75mph on the freeway with my sister's CS ('94 3100) before i got mine. The Service Engine Soon light was even on, as was the A/C!

 

She still to this day claims she gets like 26-28 mpg on her trip to work (back roads and some city traffic)

 

Maybe the 3100's injection system is worth more mileage?

[phantomshado]

I just did a roundtrip potsdam to buffalo, which means a few hours on I 81 and some I 90 (fucking thruway) which means speeds anywhere from 65-85. I pegged my full needle leaving town and drove 483.6 miles by the time my check gauges light came on. I figure thats about 520ish miles to a tank at nearly exclusive highway speeds, therefore about 32ish mpg. Not too shabby. I didn't run the ac, but I like the wind when its nice out, so its not an issue.

[Lee]

I used to have an 84 Plymouth Turizmo (dodge charger/glorified Omni) with a Pugoet 1.6 liter pushrod engine and it got.......no lie or embelishment.......46mpg on the freeway. To this day I can't understand why our milage still sucks in every car out there. 46mpg with a 4 speed and a bit of nice power there also. It would do in the 36 range for town.

 

You'd think that in 20 years they could make that a steady number not some weird fluke.

 

My Regal 26 mpg with 35 mile one way trips and a bit of town cruising.

 

Vibe has been 32 consistantly with the same perameters. It has a 1.8Lt. 16 valve 130hp motor. Variable valve timing.

[93CutlassSupreme]

I used to have an 84 Plymouth Turizmo (dodge charger/glorified Omni) with a Pugoet 1.6 liter pushrod engine and it got.......no lie or embelishment.......46mpg on the freeway. To this day I can't understand why our milage still sucks in every car out there. 46mpg with a 4 speed and a bit of nice power there also. It would do in the 36 range for town.

 

You'd think that in 20 years they could make that a steady number not some weird fluke.

 

My Regal 26 mpg with 35 mile one way trips and a bit of town cruising.

 

Vibe has been 32 consistantly with the same perameters. It has a 1.8Lt. 16 valve 130hp motor. Variable valve timing.

 

look at the Model T Ford. got better gas milage than half the cars out there today.