Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Brake and Clutch fluid

Just been to Halfords to replace my existing Halfords Uinversal Brake and Clutch fluid DOT4 container. They didn't have any of their own, so suggested that I buy DOT4 ESP Synthetic. Will this be ok, as there is no mention of synthetic on the old container.
Geoff Mears

not sure, ESP is for use in vehicles with (ESP) Electronic Stability Programme

the number system isn't always a guide to how good a particular product is, i.e. a good quality DOT4 *might* be better than a poorer quality fluid rated at DOT Super4 (DOT 5.1)

IIRC the Spridgets were originally on DOT3 but most owners accept the use of DOT4 (but don't apply the same updating logic to oils)
Nigel Atkins

Chemistry .... oh boy!

Ive been using castrol LMA the past several years in all my stuff with good success, its rated DOT 4 and is considard as a synthetic

That said... id read that can over with a fine tooth legal file and be very wery of anything that says silicone or dot 5.1

Worse case senerio you maybe cleaning your entire brake system internals with a Q tip and denatured alcohol.

Your wise to question your indecision

Prop and the Blackhole Midget

The DOT codes are illogical Spock!!!

When Silicone came out it was called DOT 5 so we would all know it is not the same as DOT 4, but DOT 5.1 is NOT Silicone, it's like s super DOT 4.

Anyway, there could be as much discussion about Silicone fluid as there has been about FWB's and Oil Sucking.

I Use Silicone DOT 5 in preference to DOT 4. You are right that they are not compatible but you don't have to remove every molecule of DOT 4 before you use DOT 5. Just make sure you clean as much DOT 4 out as possible, and change your cylinder rubbers too. That's a good idea anyway when you do a rebuild.


Rob aka MG Moneypit

Could be wrong on this but my understanding was that silicon based fluids were for competition not road use. I thought they had very limited life due to more readily absorbing atmospheric moisture, which in turn dissolves more air leading to reduction in efficiency as a hydraulic medium as the dissolved air increases compressibility.
So they're great if you change the fluid frequently, but not otherwise.
As a side note I never allow anything containing silicon near my car or boat as it contaminates any surface it touches and makes it impossible to paint thereafter.
RS Hughes

just for peace of mind I'd suggest that if you had no problems when using the previous Halfords Universal Brake and Clutch Fluid DOT4 then use that again, go to another branch and swap out
Nigel Atkins

I have been using silicon brake fluid for more than 25 years and have never ever had a problem caused by it. No cylinder deterioration or wear in normal service. Silicon fluid doesn't act hygroscopically - it is normal brake fluid that absorbs water from the atmosphere; that is one of the primary advantages of Silicon fluid, plus the fact it isn't corrosive if you have a leak or spill.

I know a lot of people who also use it and all are happy with it. It seems to me most of the problem tales are from people who have never used silicon fluid, or are trying to patch up a brake system that isn't in top condition anyway. I won't let normal brake fluid near my car. After 20 years of service I replaced the master cylinders, braking cylinders and clutch slave and found all looked pretty much like new inside and outside!
dominic clancy

Unipart sell (sold?) a glycol, non-synthetic DOT 4 clutch and brake fluid:

Not sure how to buy Unipart products direct now many of the Unipart stores have gone, or some turned into EuroCarParts branches.

M Wood

Looks like Morris sell a non-synthetic DOT 4 too:

And Valvoline:

M Wood



And EBC:

Note that many brake fluids are made by Orthene (EBC's is). See

Fascinating world!

M Wood

In a word -- NO
The shopkeeper is wrong
Dot4ESP synthetic will not mix with your Dot4
If you were flushing the whole system and replacing rubber cups including the master cyl, yes you could use synthetic fluid but if not you run the risk of the cups etc swelling and causing problems
If you just want some fluid for topping up the Dot4 already in your car you need to stick to non synthetic Dot3/Dot4 Glycol based fluid--------
William Revit

Thanks everyone.
Geoff Mears

This thread was discussed between 28/02/2015 and 02/03/2015

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.