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MG MGB GT V8 Factory Originals Technical - Synthetic Oil

Time to drain the break-in oil from the freshly rebuilt Rover 3.5L V8. Any reasons not to use a synthetic? Any real experience?

I've never a synthetic before. Several years ago, I was planning to use Mobil 1 in an airplane. The reasoning was that it held up better when used infrequently. Private aircraft spend most of their time just sitting around. I never did change though, and then Mobil had a class action lawsuit against them for damage to aircraft engines.

I assume that things have changed since then. Hot Rod magazine frequently uses synthetics in their projects. The MGB will be a driver, but not a daily driver so it probably won't make 3000 miles per year so I could change once a year instead of every 6 months.


Edd Weninger

Phil Dooley's car
Edd Weninger

I have used synthetic on my factory V8 for the last half dozen years or so. I have never had any problems with it when it was used daily, and now, used very infrequently, still no problems. It was not Mobil though, it was Comma, Syner-G.
Murray Cowley

I was told by a machinist just be sure the motor is thoroughly broken in, that if the rings haven't seated that they won't with synthetic oil.

I really wouldn't use a fully synthetic oil in an old design engine such as the 3.5. The clearances in older engines are not like those on moderns and you could find an increase in oil consumption. As John above says definitely don't use it on a new rebuild. and I would be very reticent to use it in an engine with high mileage on normal oils. Many a story of bearings been run after a change to a high detergent synthetic such as Mobile 1. IMO frequency of oil change is far more important than the synthetic/non debate + a good filter with an anti drain back valve.
Neil Cotty

I fully endorse what Neil says.

An oil and filter change every 6 months or three thousand miles.

It seems generally agreed that 50% of wear on engine components occurs during the engine start-up, before oil pressure can be established by the oil pump.

If you are really concerned consider installing a pre-oiler such as Accusump, which will also protect against oil surge:-

Safety Fast


Nigel Steward

My engine has now done 140,000+ miles. I had no problems with increased oil consumption at all. IMHO the engine ran better. Of course I changed the oil regularly at or about every 3000 miles.
So there you go. Every one has their own opinion ref the merits or not, I can only say what my experience is, all good.
Murray Cowley

Synthetics like GTX Magnatec are available for both modern and 'older' engines - but you have to look closely at the packaging to spot the difference. I find it gives better hot idle (stuck in summer traffic) pressure and lower consumption than the GTX 15W/40 that seems to have replaced 15W/50.
Paul Hunt

how many use a pre-oiler and has it made a significant difference in engine wear/performance?


The Rover V8 is prone to sludging which full sythetics help to combat.

However is is far too early in the engines life to change over - I would recommend you get the first 3000 miles over, staying on a mineral oil but changing the oil every 3 months or at 1250 mile intervals - ie for the next two changes. Then change over to a synthetic - but you need to change the oil once every 3000 miles or 6 months thereafter - keep the engine clean inside and it will last - neglect it and you will be rebuilding again in 50000 miles.
Chris Betson

Thanks for all the replies. I'm encouraged by the good results that some have achieved with synthetics and I will probably use it eventually. But yesterday I put in the 'good ol' Valvoline for the first change.

Edd Weninger

Edd Weninger

I have an Accusump but I haven't started to fit it yet. I bought directly from the USA and it cost me at least 200-250 ($Alot.00) less than the cost in the UK.
I bought partly because of my cold-start rattle problem but also because I quite like gadgets.
I bought the 3 qt model with electric valve.
I haven't examined the kit very carefully yet but first impression is that it it is pretty big - much bigger than I had imagined from looking at the specs.
Particularly it is bulky and I now understand what 4 1/2" diameter really means (no dirty jokes, please). I haven't offered it up to the car yet. I had intended that it would be mounted under the front valance but I now have doubts as to whether it will fit there.
When I start working on it I will post up the story on this BBS.
Naturally I would be interested to hear from anyone who has any experience of these units.
Marc Gander

Here are some links with Accusump info


This thread was discussed between 15/02/2003 and 25/02/2003

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