TR2/3/3A Poor MPG

[Scotsman]

I am getting 17 mpg with city/freeway driving. I have been told by local TR3 drivers I should be getting significantly better milage.

Q
Should I be expecting to get better mpg to the point I spend money troubleshooting, or just live with it. If I can get sig better milage, minor work would be recouped over time through less $ spent on gas.

Details below:
Premium gas
New Plugs NGK B6H S
Electronic ignition
Tyres inflated to 36 front, 34 back
Carbs serviced
Runs and starts well with no blue smoke
1 qt oil /1000 miles
Compression 130, 130, 135, 135
92K miles on engine, and don’t know if there has been an engine rebuild at any time.

It has been suggested I have distributer checked for advance curve, and also see if the correct needles are in the carbs.

 

[NutmegCT]

My 1959 TR3 gets 20-25mpg depending on the type of driving. For me, 99% of my driving is twisting country roads here in eastern Connecticut. I use regular gas, points, adjusted carbs, tires 30psi front and back, and compression is similar to yours. Have no idea how many miles are on the car, and I doubt the engine was ever rebuilt.

Your 17 mpg seems low - but what type of driving do you do? and how do you measure your mpg?

Edit: my driving is mostly 45-55mph, over rolling countryside.

Tom

 

[trglory]

Back in 1958, most TR3 drivers expected over 30 MPG (highway) on regular gas. But that was 1958 BC (before corn). It's generally accepted that MPG has been seriously degraded with the newer additives. Write to your congressman and tell him that corn belongs in whiskey, not in gas. Now on the other side of the coin, if you put 1,000 miles a year on your TR3 it hardly seems worth worrying about miles per gallon, concentrate instead on smiles per gallon.

Joe

 

[LarryK]

As Nutmeg says , alcohol reduces mileage. Make sure tune is good, tires aired properly, everything is oiled and greased as it should. Tune according to fuel and driving conditions and go for the best. To measure MPG more precisely, use same pump for a few times and go for a couple tanks then average.

 

[TR3driver]

Driving style makes a big difference as well. I've never averaged more than about 21 (usually less than 20) mpg commuting to work (mixed city & highway), even though I get close to 30 on long trips.

You didn't mention mixture adjustment; you could try leaning it out by 1/2 flat on each carb and see what happens. Most people seem to set them on the rich side. Also check that the vacuum advance is actually working; and that the jets are always returning all the way against the mixture nut when you release the choke.

 

[Scotsman]

Forgot to add one detail. Vacuum advance not working.
I measure gas consumption by going through 2 tanks of gas, filling tank (at same station) to top, noting milage, and gallons. Most accurate way I have found.
Driving style average, including local streets, country roads and occasionally Freeway. Shift up between 2500 - 3000 rpm.

 

[TR3driver]

Forgot to add one detail. Vacuum advance not working.

Fixing that should be good for 2-3 mpg.

 

[martx-5]

... It's generally accepted that MPG has been seriously degraded with the newer additives...

Joe

Well, I don't know about "seriously degraded". Ethanol has about 1/3 less energy per gallon then pure gasoline, although this varies depending on the amount of denaturant that is added to the ethanol. Thus, vehicle mileage may decrease by about to 3-4 % when using E10. Therefore a car getting 25 mpg on gasoline will lose less then one MPG using E10. Most people wouldn't even notice.

That said, I'm not a big fan of E10, and now we've got to look forward to even more of this stuff in the gas with the new E15 that's starting to come online. This whole push to E15 is political, so I'll leave it be except to state that anything that can adversely affect the operation of so many people's cars, should not be political.

 

[CJD]

Forgot to add one detail. Vacuum advance not working.

Well, there's your problem!

All my computer cars lost 10-12% mileage with the ethanol. That's reading straight off the computers for mileage.

 

[NutmegCT]

Well, there's your problem!

All my computer cars lost 10-12% mileage with the ethanol. That's reading straight off the computers for mileage.

John - that's interesting. What are "computer cars"? You mean the built-in MPG estimates on the digital screens?

Thanks.
Tom

 

[sp53]

If you have not, you might want get out on the freeway and check the calibration on the speedo at one of those mile post deals. Some of the odometers clog up with old grease.

 

[CJD]

Hey Tom...yes, that's what I mean. All my cars newer than 1995 models have the mpg calculated by the onboard computer. An example...my '05 Jag used to get 28 mpg pre alcohol, but now shows 24 mpg with alcohol gas. My TR3 computer is in my head...and doesn't work too well!?! If I fill the TR tank it sloshes out the vent. I never completely fill it, so I have never had a chance to figure out the TR3 mileage. I can say its nowhere near 30...but that's all city driving.

 

[tinman58]

I really don't care what I get in the MPG. It is all about the smiles and fun. But on the way down to Big Bear for Triumpfest I got 22 mpg running at about 70- 75 mph, and a few times 105 mph.

 

[TR3driver]

This whole push to E15 is political, so I'll leave it be except to state that anything that can adversely affect the operation of so many people's cars, should not be political.

I would agree, but unfortunately the availability of any fuel at all is already political whether it is blended with 'shine or not.

It would be good, however, to run to ground the reasons why some people see only 3% drop in fuel mileage with E10, while so many others report several times as much. Some of that I am sure is wishful thinking (on both sides) but I think there must be something more going on. For example, here is a test that shows only 3.6% drop in highway mileage, but 7.9% in city mileage.
https://news.drive.com.au/drive/mot...-v-e10-v-premium-unleaded-20110205-1ahgx.html

One theory is that it changes the flame propagation speed, reducing overall engine efficiency. Or it may be something even more subtle than that. I used to own an Audi 100LS that got noticeably better fuel mileage running one particular brand of premium gas (Amoco unleaded) but still ran fine (no knocking or anything) running any brand of regular or premium. The Amoco had some sort of strange additive package, because it left purple stains around the spark plug threads. (No, I am not kidding.)

 

[NutmegCT]

Several members have referred to ethanol blends as producing "less horsepower" than non-ethanol gasoline.

Wouldn't that affect "miles per gallon"? In other words, if you used 1 gallon non-ethanol to drive 30 miles at 60 mph, would you use more - or less - ethanol blend gasoline to go the same distance? Would you be opening the throttle more to keep at 60 mph for the 30 miles?

Thanks.
Tom

 

[TR3driver]

Wouldn't that affect "miles per gallon"? In other words, if you used 1 gallon non-ethanol to drive 30 miles at 60 mph, would you use more - or less - ethanol blend gasoline to go the same distance? Would you be opening the throttle more to keep at 60 mph for the 30 miles?

Yes. Pretty much everyone agrees that you burn more fuel for the same distance (or ultimately get less power at full throttle). The only question is "how much less".

Theoretically, the difference should be only about 3%. So to follow your example, 1.03 gallons to travel 30 miles or about 29 mpg. Hardly enough to argue about.

But lots of folks have reported getting 5% or even 10% less, which makes the ethanol a total waste of time. John's example above (28 mpg vs 24 mpg) suggests that he can actually go farther on 0.9 gallons of real gas (0.9 gallons times 28 mpg is 25.2 miles), than on 0.9 gallons of gas plus 0.1 gallons of ethanol! Since the whole point of adding ethanol is to reduce the amount of petroleum used, and to reduce the amount of CO2 emitted; this obviously makes no sense at all (especially since ethanol costs nearly as much as gasoline does).

 

[Jerry]

You were doing 105 in a TR3??? I am amazed. I hit 94 in our old TR3A and I could not tell which way the front end wanted to go. Decided it was unsafe. The TR3A that I am working on now, should do better since it has a sway bar and rack and pinion steering. Can't wait to try!!!

Jerry
Almost done
TR3A 1960

 

[pdplot]

Back in 1956-57, my TR3 consistently turned in about 30 mpg. Even better than the MG TD because the engine wasn't working so hard. My TR6 now averages around 24 but I haven't checked it lately. I just don't drive it that much. I have to use 93 octane though.