gas milage comparison

[rjfranken]

I'm wanting to figure out if I can improve my MPG. Using the Reatta as a daily driver I get 1 week out of the full tank. Same driving in mt 3.8 V6 '91 merc sable I get 2 weeks of driving; and it weighs 1000 pounds more. And yes, I have a new O2 sensor. Both tanks are the roughly the same size.

Instant milage reading on the freeway at 60 is between 17 and 27 depending on hills. I have seen 31 on some flats at 70.

Usual?

[2seater]

The mileage range sounds about normal, although steady highway speeds shouldn't be in the teens. As the % of alcohol is increased in normal gasoline, the mileage will drop by some amount. Same fuel stops? What is the actual mileage calculated from usage vs measured miles? I have owned more than one Taurus/Sable and the normal fuel mileage has been similar to my Reatta. I doubt the Merc weighs 1k pounds more than the Reatta, unless you are comparing the gross vehicle weights on the door, which includes cargo and passengers? The Reatta weighs more than a LeSabre of the same year, but has a very limited load capacity.

[johnemac]

I found a "light foot" while monitering the trip computer offered the overall best increase of my mpg. Spray cleaning the throttle body and it's air sensor weekly was second. My 90 has no trip computer and I miss it in that regard.

[padgett]

Driving conditions make all of the difference, if I really cared about mpg, I'd drive the Fiero more. Fact is that the Reatta is both heavy and has a big (nowadays) engine.

With everything optomised I have averaged 27 mpg on a 100 mile run to St. Augustine but that was all freeway/no stops or even slowdowns below 50 & mostly on cruise.

What kills MPG is cold starts, short trips, and stopsigns/lights. In an average week I may never get on a freeway or any limit above 45. MPG is in high teens then.

Key is being in O/D-lockup as much as possible. One thing I have noticed is that am in lockup at 46 mph in the 88 but not until 52 in the 90 and both are inside factory limits.

[handmedownreatta]

my brothers v6 86?fiero got terrible mileage.it may have needed work.

[padgett]

I have gotten below 1 mpg with a Corvette but that was 1/4 mile at a time, all depends on condition, tune, and driving. If you want really good mpg you need a 1000-1500cc diesel in a 2,000 lb car but that is unAmerican. Even Hybrids here have engines that are too big (should be under 1000ccs).

Was just comparing my 86 Fiero V-6 (22-24 mpg) to the Reatta (18-27 mpg) - Fiero would do better since a liter smaller and 1,000 lbs lighter but is not geared for economy, 2600 rpm at 60(about 1,000 rpm higher than the Reatta) and a Chebby engine.

[handmedownreatta]

i just rechecked my highway mileage while going after some new wheels.im down to 25.8 mpg at 72.at one time i was getting 28.

[padgett]

Tire pressure is critical, must be over 32 on all 4. 35 is good. Under 30 can cost 3 mpg at speed.

Edited December 2, 2010 by padgett (see edit history)

[rjfranken]

Some good tune tips!-does that K&E filter help breathing?

[JalopyBob]

My 90 gives me 19mpg around town and 27-28 on the highway under normal driving conditions. More spirited acceleration can reduce those numbers.

[handmedownreatta]

my new tires are 55 psi max.what pressure should i run fof maximum tire wear?225/55/16

Edited December 3, 2010 by handmedownreatta (see edit history)

[padgett]

Good question. If on 7" rims I suspect around 35 psi. I really do not understand this change in tires where the pressure goes up but the load stays the same. Would think that the load was a pressure vs volume thing so for a given size, the max load should change as pressure goes up.

[rjfranken]

I've herd plus 25 percent of max. 2 seater, hows that air filter working out?

[handmedownreatta]

my new tires are 55 psi max.what pressure should i run fof maximum tire wear?225/55/16

i looked again.they are 44psi max.i set them at 35 for now.

[2seater]

I've herd plus 25 percent of max. 2 seater, hows that air filter working out?

Are you asking about the K&N cone filter I use? I have had that for years in several different configurations, including ahead of the turbo, and the one in the pic is just slapped on when I reinstalled the original engine. Surprizingly, the filter actual picks up little heat from under the hood, at least when the ambiant was about 50*. It does rise to around 12* above ambiant at slow cruise, like 25-30 mph in traffic, but actually dropped to only one or two over ambiant when at highway speed. My engines have not been completely stock for many, many years, so I really can't comment on mileage or performance attributes. It is simply a convenient filter to install as I fiddle with things.

[padgett]

But a Magnavox ignition ?

[2seater]

But a Magnavox ignition ?

Yeah, I know. The coil pack is actually supposedly an upgrade unit sold to the GN guys, but no way to prove if anything special or not? I have never found a need for anything more. I can't say the later model Delco units aren't better and even though I plan to give it a try, I just never got around to it. Too durned cold to do the junkyard thing now and the car is sleeping awaiting a different style turbo installation, similar to the Volvo V6 setup from the late '90's thru early '00's.

[padgett]

Heard of Jacobs coilpacks but was $110 and started finding Delcos for $20-$40 with replaceable coils.

[rjfranken]

Are you asking about the K&N cone filter I use? I have had that for years in several different configurations, including ahead of the turbo, and the one in the pic is just slapped on when I reinstalled the original engine. Surprizingly, the filter actual picks up little heat from under the hood, at least when the ambiant was about 50*. It does rise to around 12* above ambiant at slow cruise, like 25-30 mph in traffic, but actually dropped to only one or two over ambiant when at highway speed. My engines have not been completely stock for many, many years, so I really can't comment on mileage or performance attributes. It is simply a convenient filter to install as I fiddle with things.

Yeah, I can tell. Can these heads Be ported any much (free horse power) besides the gasket "lets?

Pls. Someboby say "Oh Yeah!"

Edited December 4, 2010 by rjfranken
"I" can tell (see edit history)

[Guest squiretom]

no freeway driving and mainly 55 mph stretch and a light foot , never get more than 18mpg on my 91. must be the higher gear on 91's. @1800 @60mph on 16 inch wheels, lockup comes in at about 46 mph.

ethanol is a mileage killer.

[jonlabree]

In a previous post................

The supercharger was ported and polished, as was the heads and the headers.