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MG TD TF 1500 - octane level

I just did a search on "premium gas" and "high octane" in the archives and got a fairly confused set of results. I just filled the TD for the first time at a gas station (another first) and put in mid-level octane fuel (My choices here in AZ are typically 87, 89 and 91 octane gasoline).
For any of you guys who have been driving mostly unmodified TD's, what do you recommend? I know for heavily modified heads you probably want higher octane; but on an unmodified engine, isn't it better to at least stick with the 89 octane fuel instead of 87, now that the antiknock additives are gone?
On another note, some time ago I happily reported that the fuel tank warning light actually worked... but when I filled the tank, the light stays on ... oh well :)
Geoffrey M Baker

The requirement is really based on what compression the engine has. A stock head (doubtful if you could find one) is a fuzz over 3" thick. The ratio with that was about 7.5 to 1. Over the years almost every head has been shaved..for various reasons. Quite often to bump up the compression and the horsey power with it. Unless you are getting up around the 9 to 1 figure, the mid grade or lower should do just fine. If you hear some valve clatter while pulling full throttle try the next grade up.
MG LaVerne

I store my defueled TD each Winter in my basement for several reasons. When I add gas in the Spring for the first start-up, the fuel warning light sometimes stays on. But with a little driving and bouncing the fuel around in the tank, the float switch begins to do its job. So, maybe yours is just temporarily stuck and will get jarred loose soon. All is not lost Good luck!
Jim Merz

I won't keep my fingers crossed, Jim, but if that happens I'll be pleasantly surprised. In the meantime, I'll just rely on the measuring stick :)
Geoffrey M Baker

Have you rebuilt the dash?
You may have left out the insulating washer and grounded the warning lamp to the panel
Test: undo the wire at the tank gauge, if the light stays on, the lamp is grounded to the panel. If the light goes out the problem is in the tank gauge.
Don Harmer

We run a supercharger (which almost never gets up to 6psi boost) and use 87 Octane with no pinging issues.
JRN JIM

I was told that the XPAG engine could run on almost any fuel from almost varsol to premium. So with fuel being $135.00 per litre here ( approx. an american quart) I just stick with the lower octane stuff.

Having read LaVerne's comment I just might put some mid-grade in the next time and see if it cures the rattle.
C.R. Tyrell

CR,

Don't you have the decimal in the wrong place.

Jim
James Neel

Lol, CR, I am NOT moving to Canada at $135 a litre!!! :)
Geoffrey M Baker

I use 87 and run a lead additive with each fill up.


CJ Henderson

My advice is to leave the poisonous lead on the store shelf?.hopefully enough people will do this so it will no longer be manufactured. There is no need for it in our cars. Total snake oil. Regards, Tom
tm peterson

There are a LOT of articles addressing the effects of lead poisoning as a result of gasoline lead additives. Here is an excerpt from just one..the last line is chilling. ..regards, Tom

..."No safe threshold for lead exposure has been discovered—that is, there is no known sufficiently small amount of lead that will not cause harm to the body...."

For the health of your family, friends, neighbors..anyone who breathes...Leave the poison on the store shelf.
tm peterson

Good advice, Tom!
Geoffrey M Baker

CJ,

Looks like that lead additive blew the tub right off your chassis.

Another reason to not use it.

Jim
James Neel

Using 87, no additives, no pinging, 9.1:1 compression. Bud
Bud Krueger

HOLY CRAP @ $540.00 a gallon it better come here, put itself in my tank, and give hundreds of miles to the gallon, or I wouldn't be going anywhere but downhill! LOL

I run hi-test and get better mileage from it.

Travelled with a gent that always went out of his way when we were near West Virginia to buy this "super cheap gas". The van we were in got about 350/400 miles to a tank with "real gas" ...about 250 with the "bargain gas", and you could hear the valves floating. Four motors in 2 years was (IMHO) not a big selling point either to saving a few cents per gallon.
David Sheward 55 TF1500 # 7427

Tetraethyl lead has been pretty much banned. There are other lead substitutes that HOPEFULLY protect valves/seats similar to lead.
JRN JIM

Good day all:

Topped up the TC on May 30th., past, at our local Petrocan station and paid $ 1.47 Cdn./litre for 87.

I usually use Chevron 94 sans ethanol. The last time I bought that was July 08, 2013 at $ 1.57/litre. I shudder to think at what is being charged for it at present and I'm too cowardly to enquire.

However; after paying that price, I reckoned, all the hype over ethanol, water separation and its subsequent settling to the bottom of the tank, there to reek further havoc in inflicting rust damage, regular 87 would just have to suffice.

Anyhow; both petrol forms, to lessen engine damage, require the use of a lead substitute to be safe, don't they ?

And of course, now one must also factor in the dreaded ZDDP crisis.

Is it getting to the point where we may just have to sit in our cars, in the garage, with one of those Hollywood "roll by's" playing, simulating travelling ?

I know way out of bounds, right !
Jack Emdall, TC6768/TD3191, Halfmoon Bay, British Columbia, Canada.
Jack Emdall

jack, ZDDP additive is not necessary for the XPAG..modern oils have ZDDP in them..albeit at a level lower than their peak levels..(and additional anti scuff additives old oild did not have) professional mechanics advise unless you are running a wild cam profile with high spring pressures you don't need ZDDP in an XPAG.
the lead additive was a myth that finally died of natural causes years ago in trade publications..it still will float around occasionally on amateur forums from time to time...leave the poison on the shelf. octane rating is octane rating no matter what chemical compound is used to raise the octane rating. 87 octane is more than the cars were designed to operate on. note Bud's post above regarding a 9.1:1 compression ratio engine. regards, tom
tm peterson

OOOps.. Decimal in the wrong place. $1.35 per litre. Still way too expensive.
C.R. Tyrell

Geoffrey-- Regarding the low level light, may I offer a comment based on past experience? I had a similar problem that started only once in a while and finally progressed to the light remaining on all of the time. I could find nothing wrong with the wiring so I replaced the fuel sending unit in the tank. I could not find anything wrong with the old unit. The new unit worked great for a couple of months and then the problem returned. By this time I was getting pretty good at removing the fuel from the tank to get the fuel sensor out but it was still not what I call fun. I removed the sensor and, as before, it looked just fine. As I was putting it on the workbench something caught my eye on the plastic float. Sure enough, it was filled with petrol. I checked the old unit and it too was full of petrol. I ordered a metal float to replace the plastic float and, at least to date, all has been fine. This was a couple of years ago. My lesson was to never use the plastic floats but only metal floats.

Larry
LD Kanaster

Don, your advice re my fuel warning lamp was a good one. Knowing me as I do, I knew it was entirely likely I might have left out the insulating washer :)
So while it was still cool this morning I undid the wire to the tank sensor.

Sadly, the light went out. So the circuit is good, and that means the fuel sensor arm is stuck. (or something else is wrong with it). The solution is to wait and hope that as I drive Lily Christine IV more and more, she will become unstuck. If after a few months, the light is still permanently on, I'll have to buy a new sensor, which are perfectly reasonably priced at $53 at Moss Motors. Or of course, I can play around and try to repair the existing one.

Anyway, thanks for the advice!
Geoffrey M Baker

Geoffrey Baker:

Consider joining the Roadrunners Club here in Arizona. We have several people that know the details of the MG series.
Ralph Cacace

It is also possible the flimy contact strip is out of whack. Those are very simple to clean up and adjust. A shot of carb cleaner or touch of acetone will dissolve old fuel gunk in the hinged joint.
JRN JIM

Owned my TD which is totally stock, for 37 years and always have run the lower octane gasoline with no issues but unlike many on the forum I do not run the engine continually at over 3500 RPM to minimize stress and wear.
John Quilter (TD8986)

My dad, 91, mentioned he bought a model T for $10 when he was 14. He had a welder add an extra flange onto the intake and he installed a second carb that ran heating oil- it was 3 cents per gallon cheaper. He'd run it on gas until it warmed up and then switch over to fuel oil.
Maybe that's why I add straight waste vegetable oil to some of my diesels.
JRN JIM

I thought the additive was a lead substitute, not lead. Am I wrong?
R C Flowers

R C , you are indeed wrong. leave the poison on the shelf and save your self a few bucks per tankful and it can all be done without effecting your engine.

regards, tom
tm peterson

geoffrey, in regard to your first post on this thread..you mention "anti knock additives have been removed".....tetra ethyl lead has been removed..but there are many types of additives used to deliver the various octane ratings..tetra ethyl lead was just one of these..( even at the time they were developing additives to increase octane ratings there were several scientists who were working on the additives who protested the use of what they knew was a lethal compound...but it was more expedient to use tetra ethyl lead at the time so that is how it ended up in our fuels..and subsequently our air.)
87 octane is sufficiently high octane that you will not have and detonation in your standard configuration XPAG. regards, tom
tm peterson

This thread was discussed between 09/06/2014 and 26/06/2014

MG TD TF 1500 index

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