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MG MGB Technical - Castrol 'Synthetic' GT-LMA Brake Fluid

Has anyone used Castrol's new 'Synthetic' GT-LMA brake fluid, and is it compatible with the older Castrol GT-LMA product?


Larry C. '74 B/GT & '69 midget
Larry C '69 Midget

I came across this issue a few months ago. The "new" Castrol LMA Synthetic is the same as the old. New packaging. I spoke with a Castrol rep who told me this. He also said it has always been synthetic fluid the only other change he said is that it has a higher boiling point. So it is compatable with the original LMA... I was VERY worried when I saw the new packaging as Castrol LMA is all I have ever used in the past 25 -30 yearw. There is alot written in the archives on the brake fluid subject.
MK Mike

I, too, have been using Castrol LMA for over 30 years and was concerned to see that it was now marketed as Synthetic. Having just replaced all the brake lines, wheel cylinders and calipers on my '67 B I purchased the "new" synthetic Castrol fluid and have no complaints. RAY

Whe I was in the auto parts store the other day, I noticed that all the brake fluid (DOT 3 and 4) had "synthetic" on the bottle.

I called Castrol also...same Dot 3/4 as always...improved boiling point...a new company that changed the packaging...I told them it was VERY silly to put "Synthetic" on a non-synthetic product...I told them synthetic is supposed to signify Dot 5...not sure they understood! LMA is still OK to use...
Bob Doc
Bob Dougherty

"Silicone" signifies Dot5, no?
David Lieb

yes...until now!!! The new company that bought Castrol has labled their Dot 3/4 LMA as "synthetic" as it isn't a pertroleum is NOT Dot 5 synthetic...confusing yes...silicone is Dot 5 and always refered to as synthetic but as you say...silicone is the only Dot 5 synthetic!
Bob Dougherty


Thanks for the clarification, I'm still waiting for Castrol to send me an offical e-mail response to this question. One other interesting bit they added to the label, and I quote, "you may notice a different odor, and colour to the new GT-LMA due to the new formula."

I've yet to open the new bottle, but as far as I know the old formula was clear when first opened, and I can't say I ever detected an odor. You've got to wonder if it's the same product who is screening the packaging at Castrol?


Larry C. '74 B/GT & '69 Midget

Larry C '69 Midget

Looks the same, smells the same, tastes the same.
It's the same stuff, as good or better than ever...
MK Mike

This thread was discussed between 27/09/2008 and 30/09/2008

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