70+ MPG Paseo Development

     Here I will document the progress made on the 70+ MPG Paseo. Everything will be listed in reverse order so the newest news is always at the top.


     Today I hit the next stepping stone, 70.8 mpg! There have been no changes to the car, but I did run the car lower on fuel this time. I think this helped a bit due to driving more with less weight in the car. So, the next goal is now 75 mpg.


     Continuing the quest for ever more mpgs, I installed a switch to electrically shut off the alternator. This takes the load off the engine and allows you to use that extra power for acceleration. With this modification, the alternator is simply turned off, but it still spins.

     First, I found out where the alternator field wire enters the cabin. I really didn't want to be running more wires from the engine bay back into the cabin if I could find one that was already inside. I cut the wire and spliced in a switch I had. The switch simply kills the signal to turn the alternator on.

     A very important part of this setup is using a deep cycle battery instead of running a normal starting battery. Since the car is running only off this battery, it needs to hold a charge for a prolonged duration of time. A normal starting battery will not work in this application. I used a group 24 deep cycle battery (70-85 Ah), and just fits in the engine bay. I had to finagle it around so it wouldn't hit the hood.

     The disable switch seems to make a sizable difference in engine load at idle. I have a youtube video here that shows how the switch effects idle.


     It has been done! 66.5 mpg!!! No small jump to just above 60, this was a leap. I am quite happy.
     Just previous to this you can see I had an even better fill up. I had discounted it because it was a very small fill up of only a few gallons. This leads to a huge margin for error due to variation in fill when the gas pump shuts off since I only fill to the first click on the pump.
     So, will I stop here? Nah, theres much more to be done and I think I can squeeze a fair bit more out of the paseo. So, I have renamed the title. From now on, I'll just round down to the nearest 5 mpgs. So, for now, it'll be the 65+ Paseo project.


     Next on the list, I installed an MPGuino. It is basically a open source MPG gauge that was developed by a user on It measures the injector pulses and the speed sensor to very accurately calculate mileage. I decided to add this since the scangauge wasn't working out as well as I had hoped, and because it is very inexpensive.


     Up next is another fairly decent modifcation. I swapped the wheels and tires off my 93 Tercel onto the Paseo. The Paseo normally runs a 185 wide tire. The Tercel runs a 155 wide tire. Guess which one is more aerodynamic? Now, guess which one rolls easier. The Tercel tire is the correct answer to both of those questions.
     I also picked up the most aerodynamic wheel covers I could find at the local store. Ones that tend to bubble out a little bit with less spokes are better.


     The next modification is a result of the massive grill block. I do have a scangauge that tells me the exact coolant temperature. However, I also wanted a light to let me know when the radiator fan would kick in to see if it was running too often. So, I got an LED and wired it in to the fan relay. When the fan kicks in, the light turns on. When the fan shuts off, the LED goes out. Pretty simple.


     Now, we have a very easy mod. In my opnion, this is something everyone should do. I replaced the stock manual transmission oil with a high quality synthetic gear oil. In this case, I used Royal Purple's 75W90 which is the thinnest grade Toyota recommends for the Paseo. After I swapped oils, I could noticably feel a difference in the winter when the engine and transmission were still cold. It was quite surprising the effect it made. Once the engine is warm, I'm not sure there is much difference though.


     The next thing on the list was a fairly good mod as it works out. I took a piece of coroplast (corrugated plastic) and blocked off the entire grill on the Paseo. This is an aerodynamic and heat modification. The less air going through the cooling system, the better since roughly 30% of a car's aerodynamic drag comes from the cooling system. Of course, it also helps the car heat up faster too, and a warm engine is more efficient than a cold engine.


     I took this afternoon to replace the bored out throttle body with a stock throttle body. This should lead to a small increase in low rpm torque and give me a bit more efficiency at lower rpms.

     I also removed the cold air intake in favor of the stock intake minus the last length of ducting. This should give me somewhat of a warm air intake. We'll have to wait and see how warm though. My guess is it won't be much warmer than ambient.

     The theory behind the warm air intake is it reduces the density of the air comming into the engine. Therefore, you must use more throttle to produce the same amount of power. Using more throttle decreases pumping losses and thusly brake specific fuel consumption which leads to an increase in gas mileage. It also helps increase the flame speed in the cylinder once the mixture is ignitied giving you a more efficient burn.


     The exhaust work is now done an I'm pretty happy with it, and extatic that the car is back on the road.

     I had to cut the exhaust behind the cat and reweld it at an angle to straighten it out. The last step was to cut right in the middle of the bend over the rear axle. I inserted that straight piece in the middle of the picture. The radius was a bit too sharp and the axle would hit it over pretty much any bumps.

     Just add the muffler and a bit of straight pipe out the back and we're all done.


     Its been a long time since I made udpates here, so there are a bunch squeezed into this one.

     The front brakes were quickly taken care of and there was no more hanging up. The car rolled much better, but there was still some front end noise. The next culprit? Bad bearings. I tore the hubs off, picked up parts and brought it to the local napa to do the press work for me.

     Of course with the new bearings up front the Paseo now rolls as good as new. That took care of all the extra drag and noise I was hearing.

     On to the next step, enhancing the cooling system. The goal here is to increase the efficicency of the cooling system so that I can reduce the size of the grill opening and thus improving the aerodynamics of the Paseo. My first idea to do this was to build some sort of vent inside the bumper to direct more air through the radiator instead of around it. However, once you look at the car this quickly becomes more difficult than it sounds like. The second picture shows the area from the front bumper and the radiator area. You can see getting something to seal up fairly descent would be a ton of work.

     Alright, time for plan b. Lets still improve the efficiency of the cooling system, but in an easier way. So, I looked around the radiator and saw that there are some pretty large gaps around it and the frame. Theres got to be air leaking around there. So, I took some foam pipe insulation, cut it up, and started jamming it between the frame and radiator. This will force more air through the radiator so it can't pass around it. Here are the before and after pictures.

     Finally, my mild steel 2" mandrel bent exhaust started really giving up on me. It was rusting through is so many places I couldn't keep it together for more than two weeks at a time before it broke again. So, it was time to find a replacement. I finally found a nice OEM stainless setup on ebay for pretty cheap. Well, I now know why it was cheap. It really doesn't fit to well and I'm still struggling with getting it tweaked in.

     As of right now, the car has been off the road for quite a few months waiting for me to get some time to fix the exhaust the rest of the way. However, over the summer I just barely missed my goal of 60 mpg. I did hit 59.05 twice though. A bit more work and I'll have 60 without any problems.


     Alright, lets get started. The first step is actually stepping back for a moment and looking over the car to make sure everything is working properly. You know, just the normal maintenance issues. If the car isn't running right to begin with, the mods won't be as effective.

     In my case, I have a few things that need to be looked at. The first thing is that my scangauge is telling me that my coolant temperature is getting up to 200F. My first thought is that the thermostat must be going. It is 11 years old after all. So, I went and picked up a new thermostat from the local autoparts store. Instead of getting the normal 180F thermostat, I picked up a 192F thermostat. The idea behind a higher temp thermostat is that there is less heat lost to the coolant, less emissions, and lowers engine oil viscosity a small amount. Its a minimal modification, but since I needed one anyway, I thought I'd go with something that would help the mileage. Here are some pictures of the install. Its an extremely easy job on this engine and only took about 30 minutes.

     So, how did the new thermostat work? I'm not sure yet. With the new thermostat installed, I went for a test drive. The temperature warmed right up to around 211F which is roughly 12F higher than the old thermostat. The old thermostat was 180 and this is a 192, a 12 difference. So, it doesn't look like the thermostat was the problem. I now think that the coolant temperature sensor may be the culprit of the high coolant temperature reading. I have yet to get a new sensor installed though. I do know that the ECU thinking its running hotter than normal it will retard timing which is definitly hurting my fuel economy. We'll have to wait on a new sensor.

     The next thing I noticed about my Paseo is that it does not roll as well as my Matrix. My driveway is on a slightly incline and the Matrix rolls out of it with no hesitation. The Paseo, on the other hand, creeps along slowly and does not accelerate like the Matrix does. I also noticed some noise up front. I hadn't noticed it or paid much attention to it before, but it looks like the front brakes are hanging up a bit. I took it all apart the other night and sure enough, its time to do a front brake job.


     Time to start up a new project. The 3E-ZE is comming together nicely and will be on the road this summer. So, its time to start thinking about the next thing on the list. So, we turn to the 1997 Paseo that I have been using as my daily driver while the 1993 Tercel gets worked on. The goal, of course, is to achieve 60 mpg. But first, let me provide you with some history that got me to this point.

     About a year ago I took a job that increased my daily commute from 20 miles to around 37 miles. This is no short haul. So, I started looking into ways to increase fuel economy. I poked around the internet and started reading all sorts of things. You know the ads "run your car on water!" and such. I finally came across a few sites that were actually promising.

     The first site I found was It was pretty good and had a lot of knowledgable memebers on its forum. Not nearly all of them were even getting that good of mileage though. So, one day I messaged one of the members who was getting pretty crazy mileage (over 60mpg in his Saturn SL1). He explained a few things to me and suggested I check out a local car club whose focus is increasing mileage and hybrid vehicles. So, I went to one of their car meets. At the end of the meeting they were giving driver training to people who were interested. I gladly signed up and away I went with one of their instructors. He taught me a few techniques that I had toyed with before, but never really used. He also cleared up a bunch of questions I had. Last, but not least, he recommended me to another website.

     He recommended for me to visit, the most useful site I have found yet. This is a site dedicated to helping people improve their driving techniques to improve fuel efficiency. This is where I have gained almost all my mileage thus far. Simply changing how you drive gave me an immediate boost of about 10 mpg in the Paseo. After the driver training and reading a bit more on I had increased my milage from high 30s, to high 40s. 47.8 mpg was my first tank using these new techniques. Best of all, this new found mileage costs absolutely nothing as it simply changes the way you drive.

     Now, I'd also like to point out another site as it is the one that is going to help me get to 60 mpg. is a site dedicated to increasing mileage through car modification (they also endorse driving techniques as well). They are a great bunch of people well educated in their specialty. They have a lot of information on aerodynamics and a couple people dabbling in electric vehicles too.

     So, back to the Paseo. The Paseo is already modified by myself. The 5E-FE engine currently has a shaved and ported head, bored throttle body, cold air intake, and a header with performance 2" mandrel bent exhaust. It also has TRD springs that drop the car about 1.5". It was built to get more power out of it, and that was fun. But, things change, and now its time to get more mileage out of it.

     Now that it is getting slighly warmer out again (30-40F) I've been averaging just a hair over 50 mpg. Once summer is in full swing I expect this to get up into the low to mid 50s without any modifications. However, to get to 60 I'm going to need some modifications.

     So, lets get to the modifications already! Well, I should mention that I have done one mileage related modification. That was pumping my tires up to 50 psi. 50 psi! You might be thinking I'm crazy and ruining my tires. Thankfully, you would be wrong. With todays modern tires, pumping them up that high will not cause abnormal wear or bad handling. In fact, it actaully gives you better handling and better tire wear. If you do not believe me, believe our law enforcement in this article that they published. Cruisers normally run the maximum sidewall pressure listed on the tire for best performance. So, this was mod number one. It also happened to be free since I have an air compressor. It reduces rolling resistance which is important at low traveling speeds.

     So, whats next on the list? Well, the first thing I'm probably going to start out with is reverting back to some stock components. The bored throttle body is of almost no use to me and a few other things need tweaking. The next area to look at will be aerodynamic modifications. Mainly, I'm looking into a belly pan of sorts to smooth out the airflow under the car. This will be very important since my daily commute is 95% highway travel. I'm looking at GM's EV-1 prototype electric vehicle for some of its aerodynamic styling. After that, who knows? It'll all be laid out here though.

     So, below is what we're starting with. A 1997 Paseo currently averaging about 50 mpg. Its mileage log is also attached and updates automatically. The far right pictures are GM's EV-1.