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MG TD TF 1500 - And now.... Octane.

What do you find to be the best octane for your aging engine, and why?

I've tanked up with 93 ethanol free to help diagnose problem. Aside from being $3.15/gallon it might not be the best octane for the engine.... I truly don't know.

I will switch back to ethanol gas to test a theory, and hope to be able the stay with it.

....
MAndrus

Do you have the newer valves that allow for lower octane (unleaded) fuel? Made a big difference for me.
Christopher Couper

You only need a higher octane to account for increased compression. The stock, non milled head will do fine on regular. The problem is, most heads and block decks have been milled a few times now.
David
D. Sander

I hate to sound like a broken record on this issue but repeated bad experiences have proven to me that ethanol free gas is far superior.
1. The engin runs stronger.
2. Gas milage is better.
3. If the car is an occasional drive the storage time has less effect on ethanol free gas.
I have found this on multiple occasions with every internal combustion engine that I own.

Regards,

Jim Haskins 1953 TD
J. M. Haskins

Lazarus runs fine on regular pump gas (87). That's with a compression ratio of about 9.1:1. Bud
Bud Krueger

Don't confuse octane with ethanol. Higher octane simply retards (raises) the inviting point for higher compression. Ethanol reduces the energy available per gallon and raises the price of good corn fed beef. Jud
J K Chapin

My TF 1500 likes high octane (the 93) and would love ethanol free if I could get it. Compression ratio is 9.5 to 1!
With ethanol gas it is hard to start after sitting, and the mpg is down 12%
ad the price of serloin keeps going up.
Don Harmer

Just to go a bit further with Jud's comment, ethanol is basically just good old moonshine. Ethanol produces less BTU's than non-ethanol gasoline and therefore reduces your fuel mileage by a small bit. It is typically mixed into today's gasoline at ten percent. This is what the E10 sticker on the gas station dispenser is about. Since the ethanol still burns I don't think it is possible that your fuel mileage clould be reduced by anywhere near 10%, although I have heard many claims of 25% and more.

The octane sticker on the pump is completely different. The octane index is also known as the anti-knock index and as Jud said it is just a measure of how resistant the fuel is to igniting before you want it to due to high compression for example. If you look closely at the Yellow with black print sticker on the pump that says 87 or 92 you'll see in tiny print, "R+M/2 Method". These are the two methods of indicating the octane index in the USA. R is the research method. If you want a good explanation of this method you'll have to Google it because I simply don't know. The other method is the Motor method. The test labs have a one cylinder motor that is calibrated to start knocking (pre-igniting) at an octane index lower than where the motor is calibrated. It is actually possible to field test the octane level right at the station using an instrument (one brand is Zeltex) that shines an infrared (I think. It may be ultraviolet), light through a sample jar of the fuel being examined.

You add R+M divide by two and there you have it. Interestingly, I read recently that some countries (eg. Australia) only use one of the two methods so the octane numbers they use there are higher than they would be in the USA with the identical fuel if I remember correctly.
Kirk Trigg

Here is a link to a publication from Minnestota's Weights and Measures Dept. that gives a better description of octane index methods and myths than I ever could.

https://mn.gov/commerce/weights-and-measures/images/OctaneFacts.pdf

You will probably have to copy and paste that into your browser.

Cheers,

Kirk

Kirk Trigg

For those of you that haven't been put to sleep by my rambling yet, here is a link to Zeltex's web site that shows their portable octane analyzer. Before the fuel is tested a black lid/cover is placed over the jar of fuel making it like a "dark room".

http://www.zeltex.com/portable/101.pdf

Sorry I don't know how to make that link so you can click it. You'll still have to copy/paste.

Kirk
Kirk Trigg

I have tracked my mileage on my 1987 Saab 900 Turbo, my 2002 Subaru Outback with the H-6 engine, my R/V with a Chevy 350 and my all-wheel-drive Chrysler Minivan. The mileage is 10%-15% less with Ethanol vs. non-Ethanol. My Chrysler burned an exhaust valve, I am convinced it is due to the Ethanol.
In addition, the ethanol gas has dissolved the rubber fuel lines on my 1970 Volkswagen Beetle. The fuel lines dry rotted from the inside out, causing the fuel tank to drain out all over the garage.
I have also had the fuel lines dry rot and leak in my snow blower, my weed trimmer, my garden tractor and my lawn mower
There are a few non-ethanol stations around, and I patronize them when I can.
This picture is of the burned valve in my Chrysler. When is the last time you have seen a burned valve in a modern car???

D. Sander

I won't use ethanol in my daily drive (a 1991 Toyota Cressida Grande) & plan to also use 98 octane unleaded in the TD, which has a CR 10.1 to 1, if I ever get it finished. Also thinking of adding a litre or two of kerosine to the tank based on the merits of kero explained in the article in the previous issue of TTT2, (unless someone tells me they're not compatible!) I'd also like to add a teaspoon of castor oil, just to bring back olfactory memories of the hot cars from my teens. Cheers
Peter TD 5801
P Hehir

Additives are good in some cases. I put a diesel conditioner in my fuel tank for my tractors. I get 3 to 4 hours more running time with it in there, less strain on the engines, more power and longer times before scheduled maintenance. I use Stay Bil Blue, Marine version, in my gas, seems to work helping the engines run smoother with ethanol gas. Non ethanol is hard to get on the road around here. PJ
Paul S Jennings

I spent half a lifetime working as an industrial chemist, some of it on designing pipe systems for fuel stations. I struggle to buy the case for adding kerosene to petrol / gas to gain some kind of benefi, that is unless I am completely missing something. What raises the octane rating of gas is lots or branched isomers or aromatics or cyclics instead of straight chain normal molecules. However in kerosene, which in general is slightly higher molecular weight (less volatile) than gasoline, the intention is usually to have more straight chain stuff in order to reduce smoke, i.e. diametrically opposed to the needs for gasoline.
I wouldn't add any castor either. Its a great lubricant in many applications, but if you add it to fuel you will just add to the build up of crud in the cylinder.
Dave H
Dave Hill

I should have also said - yes, castor does dissolve in unleaded fuel with ethanol, but it doesn't in old-time fuel without it.
Dave H
Dave Hill

Thanks Dave. I suppose as castor oil was added to racing fuels & those engines were torn down fairly regularly, crud wasn't really an issue. I was intrigued by the TT2 article on kero as the test engine appeared to run more smoothly. Any other source of branched isomers as an additive to 98 octane fuel? Cheers
Peter TD 5801
P Hehir

D. Sander. That isn't a burnt valve, something broke it. Burnt valves fairly soon leak so badly that combustion would cease and therefore stop burning the valve long before that amount of damage occurs. Rooms filled with pretty bright people design cars (and engines) to run on modern fuels. Like you said, when was the last time....?


What's with the insulation on that plug? I'm thinking the valve tried to close on a chunk of ceramic from the plug.

......
MAndrus

I bought plenty of individual isomers of C8 - C12 hydrocarbons for testing purposes and they were expensive comoared to high octane fuel (no surprise as its a blend of preferred hydrocarbons). Even toluene or xylene probably cost more.
I can't explain why the tests with kero appeared to work. Maybe Nicky Tesla could.
Dave H
Dave Hill

Kirk,
To make a link clickable just remove the "s" in "https".
efh Haskell

MAndrus,
Look at this page:
http://www.ssch.com.au/trade-news/a-basic-guide-to-engine-valve-failure/
Scroll down to the picture of a burned valve. It looks just like mine. The edges of the valve look sharp in the picture, however, upon closer inspection you can clearly see the metal has been melted away. The machine shop said they are seeing a lot of these burned valves, and attribute it to Ethonal gas. They said certain cars, like the Honda CRV are more seceptable. There was no indication of any damage whatsoever on the valve seat.
David
D. Sander

Ed,

Thanks for the tip. I'll try it next time.

Kirk
Kirk Trigg

David. Wow. I've seen plenty that were egg shaped, I've never seen a valve get so bad chunks fell off of it.

.....
MAndrus

This thread was discussed between 24/05/2015 and 25/05/2015

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