Fuel - Regular or Unleaded

[Musicman]

Hi all. I was looking through a 1975 TR6 handbook and read this about the TR6 engine (U.S.A.) and I quote, "The engine is not designed to use unleaded fuel, and whilst the occasional tankful will not cause damage, constant use of unleaded fuels will result in excessive wear which will affect the emission control system." The handbook also states that the TR6, (U.S.A.) performs efficiently on fuels of 91 octane (regular fuel). Who of you out there is putting "High Test" gas in their TR's. In my neck of the woods the medium octane level gas is 87 octane. I assume that level of octane (87) would be high enough for the engine to operate efficiently. What's your take on that?

This seems a bit odd to me considering that unleaded fuel is practically the only kind being sold now and has been for a very long time now. I can't even remember when is was that I last saw regular fuel for sale.

What do you think about this? I'm assuming that all of you are using unleaded fuel in your TR's. Am I correct in assuming this? Please tell me if I'm not.

Thanks in advance for your input.

 

[Geo Hahn]

I used unleaded for 25 years or so (TR3A) and noticed no notable valve recession when I had the head off this past summer. I got hardened seats on the exhaust valves anyway since it was off, stripped and at the machine shop.

If you're not experiencing a frequent need to adjust the valves (that could indicate recession) I wouldn't worry about it.

OTOH, octane is important and may ned to vary from what the manual says due to engine condition and what, if any, mods have been done.

 

[Andrew Mace]

So far, in three years and nearly 25,000 miles of driving in my Herald 1200 sedan, I've seen no problems whatsoever in using unleaded (premium, though, as that's pretty much what was specified for the car back then). Given that a Herald is working much, much harder than that big six in your car at highway speeds, I can't imagine that you're likely to see any more problems than I have! At worst, you might want to use a "mid-grade" (91 octane by the current rating) instead of regular, but even then it's probably only worth it if you're getting pinging.

 

[sammyb]

In terms of octane, it just depends on your car's timing and few other criteria. You'll know if you need a higher octane if you hear pinging (especially under harder acceleration, such as climbing a hill.)

As for leaded vs. unleaded, all the master mechanics I know don't use lead substitute in their own cars (including hi-po Chevys, Cadillacs and Oldsmobiles.) I don't use substitute in my cars, because I basically put so little miles on them each year that I don't worry about any damage.

 

[Mickey Richaud]

OK - I asked before, but don't remember getting a response:

Does anyone remember American Oil Company's "White Gas" back in the 50's and 60's? It was unleaded, and they claimed it would burn cleaner and was better for the car. If that was the case, then why the concern these days over using unleaded fuel in older cars?

Sign me,
"Puzzled"

 

[donbmw]

I remember my dad buying White Gas only to use it in our Coleman Stoves for camping.

Don

 

[PSUTR3B]

I too remember Amoco white gas. I think it was their hi-test gas and was more expensive. My dad dove Plymouths and I sure did not use hi-test, but I seem to remember that he used it for the mower. In my TR3B (and MG TD also) I use Sunoco 94 and no additives.
Gary

 

[jerrybny]

Yes it was AMOCO white gas. Alot of us old timers with muscle cars burned it. I used it all the time in my Firebird and my friend who had a GTO swore by it. It was very high octane. The other choice was Sunoco which I think I remember being 103 octane.

 

[TRMark]

[ QUOTE ]
I remember my dad buying White Gas only to use it in our Coleman Stoves for camping.

Don

[/ QUOTE ]
I have my dads old Coleman, I still use it. Its seems to work just fine on regular pump gas. I thought white gas was just gas without lead.

 

[Alan_Myers]

Hi,

Actually I don't find it surprising a 1975 owner's manual would talk about both leaded and unleaded fuel. Both were available at the time, with unleaded being phased in and leaded being gradually phased out.

And, if you are going to drive the car today, you won't have much choice, it will have to be on unleaded fuel.

In a nutshell, lead was added to increase the octane of fuel. Higher octane burns cooler. And, lead provided lubrication to the valve mechanisms: guides, valve faces and stems, and valve seats.

There was a lot of concern in the U.S., and elsewhere in the world, about the transition to unleaded and it's effect on the cars. It's well documented that valve guides, valves and valve seats can wear a lot faster without lead in the fuel. That's particularly true of the exhaust valves, where higher temps are more common. Thus, valve seat recession occurs. That's where the seat under the valve, machined into the head, gradually erodes. The valve slowly gets out of adjusment, is one clue that this is happening.

A car driven hard will see valve recession and guide wear faster than one treated more gently, because the "spirited" driver's engine is working harder and running hotter.

Without getting into metallurgy (not that I know much about it anyway), it so happens that certain cast iron fomulas have some natural resistance to valve recession. And, it so happens, the 4-cylinder TR's head was made with this sort of material. So, these particular engines are not prone to that sort of unleaded-fuel-related problem, if driven gently. Unfortunately, I can't say if this is true of any of the other Triumph cylinder heads, 4-, 6- or 8-cyl. Just the TR2/3/4.

Even though they wear slower than most, if apart for a rebuilt, it would probably be prudent to have any Triumph cylinder head, or any other pre-unleaded motor for that matter, exhaust valve seats worked over for unleaded use. This involves either having the existing material treated and hardened, or installing a hardened and treated insert.

Typically, upgraded valves are needed too, specially materials for use with unleaded fuel, especially the exhaust valves.

Valve guides are another story in the 4-cylinder TRactor motor, and I'm pretty certain in all the Triumph models or virtually any pre-unleaded cylinder head. As soon as practical, they should be replaced with a special bronze type that have self-lubricating properties.

Finally, some de-tuning of the engine may be needed to cope with the fact that unleaded fuel is lower octane. The ignition timing might need to be retarded more than originally. Also, engine compression might need to be lowered in some extreme examples (not very likely in an unmodified Triumph).

To give you some idea the difference fuel octane can make, just the other evening I was watching a TV show about Doolittle's air raid on Japan in 1942. They flew B25 bombers off aircraft carriers, something no one thought was possible. These airplanes typically used 200 + ft. of runway. Now they were training to be able to get airborne with under 500 ft., even 450 ft., with a load of 500lb bombs and a double load of fuel on board. In a reenactment test, the best a modern pilot could do in an *unladen* B25 was 900-1000 ft (with 2000 ft + being more typical). There were several factors, but one of the top ones he cited was that 130 octane fuel was used in 1942, while only 100 octane airplane fuel is available now.

Today's unleaded is lower octane, so, yes, I will use only premium in my TR4.

There are some "lead replacement" additives you can buy, that help a little. But, not much.. These can be found at most auto parts stores, merely are intended to help cars that haven't been converted for unleaded fuel "get by" on it for a while. Some of these both boost octane and add some lubrication properties, but most just help with the latter.

 

[Dave Russell]

[ QUOTE ]
Hi all. I was looking through a 1975 TR6 handbook and read this about the TR6 engine (U.S.A.) and I quote, "The engine is not designed to use unleaded fuel, and whilst the occasional tankful will not cause damage, constant use of unleaded fuels will result in excessive wear which will affect the emission control system." The handbook also states that the TR6, (U.S.A.) performs efficiently on fuels of 91 octane (regular fuel). Who of you out there is putting "High Test" gas in their TR's. In my neck of the woods the medium octane level gas is 87 octane. I assume that level of octane (87) would be high enough for the engine to operate efficiently. What's your take on that?

[/ QUOTE ]
Hi DM,
Two factors at work.
First;
USA octanes are formulated for the region of the country that they are used in. In my "neck of the woods" (2,700 ft elevation) low is 87, high is 92. At your altitude (5,400 ft) less octane is needed so I'm not surprised that medium is 87. Air density is less & combustion pressures are less.

Second;
Your manual likely refers to the Euro octane rating system.
There are three fuel octane rating/measuring systems in common use. The Motor Octane Number (MON), the Research Octane Number (RON) & the Pump Octane Number. The pump octane number as used in the USA is the average of the two ratings. Eg. (RON + MON) divided by two. European countries use the RON rating.

The "translation" between USA & Euro octane ratings:

USA = 87---Euro = 91---RON = 91---MON = 82.5---R+M/2 = 86.75
USA = 89---Euro = 95---RON = 95---MON = 85----R+M/2 = 90
USA = 93---Euro = 98---RON = 98---MON = 88----R+M/2 = 93

As you can see, the 91 rating in your manual is likeky Euro, & is equivalent to the USA 87 rating.

As far as the leaded vs unleaded, It would take many thousands of miles of very hard running on unleaded to cause any damage & even then damage is unlikely. I can cite a couple of very extensive tests that bear this out.
D

 

[Musicman]

I can see that premium level gas is the way to go.

 

[piman]

Hello alan,

it's my understanding that a high fuel octane level does nothing for an engines power output, but if high octane is available then the engine can be modified to increase power and run without damage. In other words, using a higher octane fuel does not give a power boost in it's self.

I must say that the power(weight reduction also maybe?) required to reduce take off distances by a quarter is very significant and sounds unbelievable?

Alec

 

[Musicman]

Okay, so maybe I'm wrong? Would I be throwing away money to put 91 octane gas in my TR when I could be using the 87 octane instead with no under--performance?

 

[Dave Russell]

If the engine has normal timing settings, 91 is likely not needed. On the other hand, since air density & combustion pressure is some 18% lower where you are than at sea level, some increase in engine power & efficiency may be gained by advancing ignition timing a couple of degrees, but 91 may still not be needed if the engine doesn't ping.
D

 

[Alan_Myers]

[ QUOTE ]
...it's my understanding that a high fuel octane level does nothing for an engines power output, but if high octane is available then the engine can be modified to increase power and run without damage. In other words, using a higher octane fuel does not give a power boost in it's self.

[/ QUOTE ]

Hi Alec,

You're right. I'm sure the difference was a higher state of engine tune that was possible due to significantly higher octane fuel.

[ QUOTE ]
I must say that the power(weight reduction also maybe?) required to reduce take off distances by a quarter is very significant and sounds unbelievable?

[/ QUOTE ]

Actually, the Doolittle flight's takeoff distances were roughly *half* what they were able to replicate in the modern reenactment, and about one quarter the "normal" takeoff roll.

There were other factors, but weight wasn't one of them. In fact, the Doolittle planes taking off the carriers were heavier than usual priomarily because fuel load was doubled with extra fuel tanks (ISTR something over 1000 gal. total). Other things were done to help offset the extra weight. For example, the two machine guns in the tail were replaced with cut off broomsticks painted black! Didn't need the weight of a tail gunner to man them, either. And, the usual complex bombsight was replaced with a simple, fixed aluminum angle sight, to save weight and because the more complex site was unnecessary at the 1500 ft. altitude that was planned for the raid.

In their favor was taking off in cool, moist air, and right at sea level. That helped the engines produce maximum power, as well as adding lift.

Another key consideration is basic carrier technique. The ship turns into the wind to launch aircraft. That can mean a gain of 15, 20 or more knots of "free speed" for takeoff. That's significant in those 1940s era airplanes that could lift off at 75-100 knots, sometimes less.

Some years ago I got a ride in this old girl, also seen here. It was pretty amazing to lift off at just over 50 mph and watch cars passing us on a parallel highway! /ubbthreads/images/graemlins/ooo.gif (The pre-flight was just as scary, with the captain climbing out on the wing and dipping a wooden yardstick into the fuel tank to check levels!). I imagine it wasn't a lot different in the B25, but I only have second hand reports from my dad, who piloted a few and loved the plane's agility compared the B29 he was usually flying.

Whoops, not much LBC content here... what were we discussing?

/ubbthreads/images/graemlins/cheers.gif

 

[Mickey Richaud]

Thaks, all - especially to Alan for the info on valve seat recession under harder use, and the quick metallurgy lesson. As to Coleman lanterns and camp stoves, when we were in our camping phase, all I ever bought was gas from the pump - was much cheaper then (wonder how much camp fuel has gone up...).

/ubbthreads/images/graemlins/cheers.gif Mickey

 

[Andrew Mace]

Good old "Lead Free Super Premium Amoco" gasoline, as it was usually known here in the Northeast. Great stuff, if you believe the many, many folk who used to swear by it. At one time, they even had print ads featuring a TR3!

 

[Tomster]

I remember white gas being sold as "Naptha" now known as Coleman camping fuel. This is a rather bizarre copy from another forum:
Does anyone know of any purpose/use for naptha?
>:
>: My father has a gallon jug in his basement. He claims
>: it was used for old blow torches.
>
>It was used in the old blow torches. I have one - a rather interesting
>piece of equipment.
>
>Naptha is also known as lighter fluid - the kind used in "Zippos".

Also, take a look at a can of Coleman Camp Fuel...

Naptha is, substantially, gasoline without any additives and with a
lousy vapor presure (gross generalization...). It pings like heck
and may lead to vapor lock in a gasoline engine, but when mixed
with naphthalene moth balls (an octane booster) works OK at modest
temperatures (i.e. don't drive in the desert...)

(How do I know? 'Cause I did it ... Coleman Camp fuel {aka Naptha}
was the only thing that could get my Honda to ping, which I needed
it to do so I could test the octane boosting ability of the moth balls...)

 

[billspit]

If you have deposts inside the engine that contribute to pre-ignition, a higher octane gas may help. The alternative is to service the head. Or as the British call it, "de-coking" it.