1983 Toyota Cressida - 18 MPG to 27+, but running out of ideas...

[gizzardgulpe]

Exposition: Back in March I inherited a Cressida from my dad, who barely drove it. The previous owner mostly kept it garaged after it hit 100000 miles, and it now has a little over 180k miles. It was in decent condition for a 30 year old car, until my dad and sister let the car sit for a couple years in the sun.

I got it running, drove it from Idaho to Kansas, and now here I am, making mods and doing a thrice-weekly commute; 120 miles per day.

I've kept a fuel log, and the worst I ever got was 18 mpg on the last leg of my trip home from Idaho, doing 85 against a 30 mph wind.

Since then, I have:
1.) replaced the camshaft housing gasket that had an oil leak.
2.) replaced and flushed the coolant.
3.) removed the power steering pump.
4.) removed the belt-driven cooling fan and
5.) replaced with a manual-control electric fan.
6.) removed side mirror.
7.) reduced windshield wiper profile.
8.) added wind shields over the porous headlight housings.
9.) added belly shield.
10.) redirected intake to capture warm air
11.) almost finished an amateur paintjob.

Still on my list:

1.) Wheel skirts
2.) hubcap covers
3.) kammback

With everything I've done so far, I can now get a pretty reliable 27 mpg if I keep my speed around 60 mph. I have a few outlier mpg readings where I went hotrodding around the local lake or needed to use the air conditioning for a trip (got over 30 mpg once, but maybe wind conditions were better otherwise?). Still, my goal is to get over 30 consistently.

So, uh... what can I reasonably expect at this point? My wife's 2000 Pontiac Grand Prix gets 32 mpg easily if I drive it like I do my Cressida, and I haven't done a single mod to it (she won't let me. I tend to break things.), which surprised me at first because the engine is considerably larger. But then again, it's all high-tech electronic and has a much more aerodynamic body than my parachute of a Cressida.

[NateHale88]

Welcome! Head on over to the garage and enter all your car specs and stuff into a Vehicle Profile. Google search all of its specs and put them into the form. People can help you more if we have this information.

Looks like you are doing pretty decent so far. Few questions.

* Have you aired you tires up to 40PSI+?
* Have you read the Sticky that tells you several ways to improve your Eco Driving?
*Do you pulse and glide at all or do a lot of in-neutral coasting?

Get a picture up of the car and we can help with possible Aero mods.BUT! The biggest mod you can do is to your driving. It takes some practice but knowing your route is one of the best ways to achieve great MPG.

Post back when your done and we can all see what exactly you have to work with! :-)

[gizzardgulpe]

Welcome! Head on over to the garage and enter all your car specs and stuff into a Vehicle Profile. Google search all of its specs and put them into the form. People can help you more if we have this information.

Thanks for the welcome.

I would post a link to the car but the anti-spam filter won't let me until I have more posts. Still, it's one of the most recent cars on the garage list.

Edit: Oh hey, it's under my name. I didn't know that was automatic.

Looks like you are doing pretty decent so far. Few questions.

* Have you aired you tires up to 40PSI+?
* Have you read the Sticky that tells you several ways to improve your Eco Driving?
*Do you pulse and glide at all or do a lot of in-neutral coasting?

Tires are properly inflated. I have been working on my ecodriving skills for about 8 years now, most of my improvements have been in the last two years, and especially since I found ecomodder.com last year. Most of my mpg boost I think has been from my driving habits changing. I've done a few experimental tanks of gas to try and get a feel for the difference in mileage for my average speeds.

However, I haven't done much pulse and glide for a couple of reasons. 1, the car loses speed very quickly when I let off the accelerator. So it's more like pulse and grind. I have experimented with a fixed throttle technique over my hilly highway commute, so I'll get up to 70 downhill and drop speed to 50 uphill, averaging around 60 mph for my 70 minute trip.

And as far as neutral coasting goes, it's a rear-wheel drive automatic transmission. I'm not super comfortable with my 34 year old transmission handling a lot of shifting in and out of neutral, plus running in neutral over 50 mph is (I am told) bad for the differential. Then again, the two places I would coast in neutral are the offramps off the highway, where my speed is usually under 50 mph anyway, so I could try that.

Get a picture up of the car and we can help with possible Aero mods.BUT! The biggest mod you can do is to your driving. It takes some practice but knowing your route is one of the best ways to achieve great MPG.

Post back when your done and we can all see what exactly you have to work with! :-)

Should be available on the garage page.

[NateHale88]

Sounds like you aren't as new as your post count defers! haha.

OK sounds like you are doing pretty good so far. My suggestion would be to figure out why the car is losing speed so quickly when you are coasting. I assume it has rear drum brakes? Often times they get old and out of adjustment and will start to drag. Best option is to switch over to disc setup in the rear which might be possible from another car with the same compatibility..... orrr the easier route is to clean/adjust and change the rears if they are too worn.

As for the automatic and neutral rear diff coasting. This shouldn't really put any extra strain on the tranny/differential. As long as the motor is running it is pumping trans fluid around and slipping it out of gear makes it similar to a manual transmission. The rear differential is constantly lubed with the gear oil so no issue there as long as your not dropping it in and out at high speeds.


I have found that with my Grand Am I can coast nearly twice as far in neutral as with the car in Drive. This works great for coming up to stop signs, exit ramps and etc, I can let off the gas much much sooner and coast much longer to the stop.

Have you changed your Gear Oil in the rear differential? Go with a synthetic, do the same for the transmission too.

Also after looking at your fuel logs I am puzzled how all the gallons are an even round number. To have an exact accurate reading it needs to be from full to empty then gassed back up till the pump turns off. How are you doing the calculations?

Example: Full tank............450 miles later refuel till pump kicks off at say 14.43 gallons........ Then take the miles divided by the gallons for exact full tank measurement

Don't know how far you plan on going with the ole Cressida but many have had good results from LRR tires also.

[gizzardgulpe]

It has rear disc brakes, actually, with a drum emergency/parking brake. I just replaced the pads in the rear and they seem to be doing fine. I should be able to test the brake theory, however, by switching into neutral and seeing how far I can coast. If I'm still slowing rapidly, it would make sense that something in the rear portion of the car is causing the drag. I had a differential gasket leak and I replaced all of the gear oil with a nice synthetic early on in my repair work. Hopefully that is not the problem.

Transmission fluid is currently a mixture of whatever the Meineke shop put in it back in March and a bottle of hard-shift lube/leak seal. It shifts into second gear pretty hard, but not as hard as it did before I put in the bottle of goop. Considering its viscosity, it's not helping my mileage, that's for sure, but that shift was scaring me.

As for the fuel logs, I keep a note on my phone every time I fill up, but I only put in the mpg for the trip. Since I can't simply backdate the mileage for the last six months, I decided to go the quick route and enter the mileage times ten, divided by ten gallons of gas. I only have a twelve gallon tank, so I usually only put between 10 and 11 gallons in the car anyway.

[Cobb]

Biggest way to get better mpg is to adjust the nut behind the steering wheel. Sounds like you are going a constant highway speed. You need to mix it up by slowing down and speeding up to add a P&G cycle to your drive.

Sounds like its at the stock height, have you considered cutting the springs to lower it and reduce air profile?

Have you done a compression test as the engine maybe warn more than it was before.

Have you checked timing, air filter, plugs and such? Have you double checked to see if a wai helps mpg on your longer trips or actually hurts it?

Is the egr clogged up or working of? Has the alignment been checked at some point?

Is the electric fan cycling or running all the time?

All these little things add up.

[gizzardgulpe]

Originally Posted by Cobb

Biggest way to get better mpg is to adjust the nut behind the steering wheel. Sounds like you are going a constant highway speed. You need to mix it up by slowing down and speeding up to add a P&G cycle to your drive.

As soon as I figure out why the car slows down so much when I try to coast, I'll add that in.

Originally Posted by Cobb

Sounds like its at the stock height, have you considered cutting the springs to lower it and reduce air profile?

This is a tricky mod because the car has a semi-trailing link rear suspension, and the wheels canter outward when the springs are compressed. By shortening the springs, the wheels will raise relative to the body and the insides of my tires will likely wear away from the extra contact. I really want to lower the car, but I would also have to alter the alignment for it, and I don't quite have the technical know-how to do it safely.

Originally Posted by Cobb

Have you done a compression test as the engine maybe warn more than it was before.

I have not. In fact, I don't know how to do that and I never thought about it.

Originally Posted by Cobb

Have you checked timing, air filter, plugs and such? Have you double checked to see if a wai helps mpg on your longer trips or actually hurts it?

The timing has been a bit of a pain. The official manual has a method for doing the timing, and when I followed that method, I lost a ton of power in second and third gear. It was too dangerous to drive in town because I couldn't pull into traffic fast enough. So I'm at a bit of a loss as to how it should be timed. Currently, I have it set to idle smoothly in drive with the brake set (maybe 15 to 20 degrees at ~700 RPM?), as if I were stopped at a stop light. Before, it felt like it would die when I came to a stop.

Air filter and plugs are new and in good condition. As for the warm air intake, I've only gotten gas once since then and it was about 1 mpg higher than before. I don't yet have enough data to see if it is making a difference.

Originally Posted by Cobb

Is the egr clogged up or working of? Has the alignment been checked at some point?

I would be mighty surprised if the engine has an egr. If it does, it's complicated and hidden away, because the exhaust manifold is pretty simple, and so is the intake.

The alignment I think was checked back in March, but I don't recall. I really only remember the problems he pointed out, and not so much the incidental stuff (and the paperwork seems to be missing. I swear it was behind the passenger seat...). For what it's worth, the car goes straight when the wheel is centered.

Originally Posted by Cobb

Is the electric fan cycling or running all the time?

I have it connected to a toggle switch on the dash. I run it when the temperature gauge gets high and turn it off when the engine cools.

Originally Posted by Cobb

All these little things add up.

If more little things are what it takes, I'm all ears.

[JRMichler]

On a car that old, I'd check the cam timing. Then check the ignition timing, not just the idle timing but the timing at higher RPM and the amount of the vacuum advance.

Check for brake drag by checking brake temperature after driving ten miles or so, preferably at highway speed. Coast to a stop, then check each drum with your hand. They should be at ambient temperature. If it's warm, it's dragging.

Manual or automatic transmission? What is the RPM at 60 MPH? What is the available power in top gear at 60 MPH? Will it maintain speed uphill without downshifting? Accelerate uphill without downshifting?

Tape some pieces of yarn to the hood and drive on the highway. If they all point rearward, you are good. If some of them swirl around in circles or point forward, there is room for aerodynamic improvements to the front end.

[gizzardgulpe]

Originally Posted by JRMichler

On a car that old, I'd check the cam timing. Then check the ignition timing, not just the idle timing but the timing at higher RPM and the amount of the vacuum advance.

The cam timing is... well, there isn't a lot of room for adjustment, near as I can tell. It's DOHC, and the cogs have markings for their positions relative to... I assume top dead center. With that in position, I adjusted the ignition timing to between 15 and 20 at ~700 RPM, and I can't even see where the timing advance goes at higher RPM. As soon as I touch the throttle, the timing mark shoots off to the left beyond the 15 degree mark and I see nothing.

I don't know how to check the vacuum advance. Can you explain the general idea so I can figure it out?

Originally Posted by JRMichler

Check for brake drag by checking brake temperature after driving ten miles or so, preferably at highway speed. Coast to a stop, then check each drum with your hand. They should be at ambient temperature. If it's warm, it's dragging.

Will do. I'll have a chance on Monday, probably.

Originally Posted by JRMichler

Manual or automatic transmission? What is the RPM at 60 MPH? What is the available power in top gear at 60 MPH? Will it maintain speed uphill without downshifting? Accelerate uphill without downshifting?

Automatic. It sits at 2200 RPM at 60 mph, in fourth with the torque converter lock engaged. I have wonderful power at this speed, and I can easily accelerate uphill without downshifting. In fact, the only way to make it downshift at that speed is to press the accelerator all the way down and trip the computer's shift trigger. It has very nice power in that band.

Originally Posted by JRMichler

Tape some pieces of yarn to the hood and drive on the highway. If they all point rearward, you are good. If some of them swirl around in circles or point forward, there is room for aerodynamic improvements to the front end.

Hey, that's a great idea. I'll do that on my next trip. Thanks.

[Cobb]

A worn timing belt or chain can have enough play that it effects performance. Same with valve clearances, do you adjust the valves on this model?

Id try jacking each corner and spinning the wheel by hand. Maybe a stuck calibrator or wheel bearing going bad.

Brake shoes drag if they are pretensioned too tight. It gives good brake response, but drags 24x7. Making them looser gives more petal travel, but dont drag.

Plan b, instead of lowering, add an air dam, lawn edge strip bottom of bumper.