mpg oddity from 1987

[Shomeyrwit]

Friend of mine had a Mazda B2000 (maybe 2200) really wide tires on stock rims, reg cab short bed 5spd std.

We drove it to Florida in the winter/spring of 1987 and I logged the mpg on the trip over, as I recall 5th gear 65 70 mph the whole way returned a fairly typical 31/32mpg. On the return trip he drove 90+ all the way up the turnpike from miami to I10 then 75 or so on 10 till near Pensacola 5th gear just disappeared, when we pulled over we discovered we only had R 2nd and 4th gears and things did not sound happy in the trans. So on the premis that I had never been stuck outside of Texas I bought 2 Mtn Dews and a six of Jolt cola topped the tank off and hit the highway. That truck had a 10 gal. tank and we always pulled over aroung 275 mi. for gas since even at 32mpg you would be close enough to empty. We drove from there past Pensacola all the way to the west side of Lake Charles at 60/65 mph in 4th gear, 410 miles and the tank took 9.5 gallons (43mpg) at that point we only had 4th gear but managed to get it rolling and out on the hwy, at the top of the Sabine River bridge on the TX border I double clutched since it had quieted the horrible noises earlier and bang ,,,, I had still never been stranded outside the state of TX cause welcome centers count, I was a caffenated mess and because it's TX a friend drove 110 miles from houston and towed us back the rest of the way.
Lots of memories from tht trip,, but always a bit perplexed by the much better mpg from 4th at 65 than 5th at 70.

[rmay635703]

Originally Posted by Shomeyrwit

really wide tires on stock rims
the much better mpg from 4th at 65 than 5th at 70.

My dodge behaves similarly at certain speeds reason being the jackhole that owned it prior to me put way oversized tires on it and then had the speedo recalibrated. (I thought they might be one size too big, nope)

Many "economy" trucks have their power band and gearing set pretty well so too big of tires messes up your FE royally since you are at too high of gearing with them. AKA you lay into the throttle more than is efficient.

4th likely put you in the right power band to get better FE, also remember if you were driving on a very slight downhill grade or had a little wind to help that also changes FE dramatically.

Cheers
Ryan

[bgd73]

I learned this very same thing with a 3 speed 1983 automatic for escort.It did better than the manul trans, while screaming at 65mph compared to a 4/5 speed.high 30s mpg.

to this day.. I associate it with an inline fours physics of demanding revs for pleasant torque (the magic spot in a cars throttle on the highway).. that very lesson, I took with me to my 90hp subaru, a 3main bearing boxer, also from the 1980s.. and made it as tall geared as possible...and it loves it. 3600 rpm = 92mph..and it could take one more realm of fuel air larger.. but I do not give it. 23 years original is the proof to go with it..

it is all the engines design. an inline has a shudder if rpms too low for demand. I have destroyed all of my attempts at owning them. My very last one broke a rod coasting down a hill with an automatic.. I am a perfect omen.I am more "dieselish" if ya know what I mean.

The fifth gear and mazda happened local here alot. no sign of it. just *poof* all done. another one was the 1980s 2.9liter ford rangers...ashame.

today, the inliners just dump a massive intake, pretending all good with gadgets of fuel injection...