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MG MGA - Is Oil Cooler necessary?

I am installing an 18V MGB fast road engine into my latest A (a Coupe), and intend installing air conditioning and an electric fan in front of the radiator. Obviously, if I go ahead with the air conditioner, then the condensor and fan will need to fit in front of the radiator. This all takes up room on the duct panel, therefore I was wondering if the oil cooler was necessary on the 18V motor?
Gary Lock

It's kind of a vague question with no correct answer unless you have more information. For common touring use most MGs will do okay without and oil cooler.

Almost from beginning of production of the MGA an oil cooler was an optional accessory. It was commonly installed on competition cars when the engine was expected to run at high speed and high power output for extended periods of time. It did not become standard on the MGA until the 1600-MK-II model. For MGB some had it and some didn't, as the philosophy was changing from streetable race car to touring car.

For cars with automatic transmission it is common to have a small transmission oil cooler inside the engine radiator. Otherwise most cars do not have an engine oil cooler. For the vintage sports cars the engine oil cooler may have been more of a marketing gimmick than a necessity for a non-competition street car.

If you want some useful information on which to base a decision, then install a temperature sensor in the oil pan (or down the dipstick hole), and drive the car in whatever manner you consider "normal" for your own use. I think the magic number for oil temperature is 250dF. Below that you don't need an oil cooler. If it runs above 250dF for extended periods of time then an oil cooler may have some benefit.

One thing to consider is that an oil cooler will most likely have zero effect on engine coolant temperature.

Barney Gaylord

Barney, thanks for the input. The reason why I ask the question is, all the 18V engines came with an oil cooler, not an optional accessory. The oil filter housing also catered for the oil cooler, so that's why I ask, "is it necessary"?
Gary Lock


Good stuff from Barney. For what it is worth I do not run one with my 18V that has been in my car for 12 years, so it is not engine type critical.

Steve Gyles

I'd look at it the other way around. Keep the oil cooler, and ask where do you put the air conditioner radiator? SOP is to move the oil cooler forward one inch if necessary, and slip the condenser radiator in smack up against the face of the engine cooling radiator.
Barney Gaylord

Gary. Not all the 18V engines came with an oil cooler. I have owned two MGBs, with the 18V engines, which did not come with an oil cooler. One of these is a low mileage car which seems to be close to/exactly factory original. On my daughter's 77B, the three year old line from the block to the oil cooler cracked as she was driving at highway speeds, damaging the rod bearings. Thus, an oil cooler is one more thing to go wrong. I would agree with Barney on this--do some form of intelligent testing, then, if necessary, consider installing an oil cooler and where to put it.

Les Bengtson

I would offer that my B has the 18GG engine with an oil cooler.

I experimented with the cooler removed one January. It made a significant difference in coolant temp and in oil pressure. The engine must have had wear at 120,000 (head was rebuilt), but it really runs pretty well

Nothing at dangerous levels mind you, but hot idle oil temp dropped to 25-30lb from 50. Running oil temp to 50-55 from 63 normally experienced. The coolant temp needle rose significantly above its normal mid position - perhaps half distance toward H.

This was with spirited driving locally in Canberra. No extended trip distances but typically 30-50K drives. I opted to reinstall the cooler.

I wonder Gary, is it worth trying the engine with cooler under your sort of usage, then without? You would then have a sound basis for deciding. Then install air et al with some confidence you will not have to rejig component locations.


Roger T


Why not mount the cooler under the duct panel and add a grille in the front valance to allow air to get to it. If you add a mounting bracket, there will be space for the hoses above the cooler, and you could also use the starter handle as well.
dominic clancy

Gary, I fitted an oil cooler to my car in June, a few weeks before I set off on the tour of the Mont Blanc region of the Alps in July.

I didnt have any particular over heating problems before the trip but it was more a question of making sure my car coped with all the long climbs over the passes that we had planned to do.

My car has no bumpers and a Sebring style front valance and so I decided to fit the oil cooler below the radiator duct panel as Dominic suggested. I cut a vent hole in the valence to let air flow through the cooler.

My thoughts were that this would leave the radiator airflow unchanged and just act as an extra engine cooling system.
( I know that the works approach was to fit the oil cooler in front of the radiator but I would have thought that this would cool the oil a little but at the same time increase the radiator coolant temperature.)

I fitted a thermostatic valve to the cooler that opens when the oil temp reaches 80 degrees C and therefore only provides extra engine cooling when it is really needed.

The car coped really well with the Alps only reaching 190 degrees F on the really long climbs up the Grand St Bernard Pass (approx 10,000 ft.)

If you decide to fit an oil cooler I would recommend that you fit the thermostatic valve so that you dont over cool the oil.

All I can say is, like Dominic suggested, that the cooler really seems to work well when it is positioned under the duct panel, especially if you cut a vent hole in the valence to let the air through to it.

Colyn Firth

Most US MGB had coolers as standard until '74, then it was deleted, along with the power. If anyplace calls for a cooler, it would be Australia and the US Southwest.

Oil temps should not exceed 220F for long periods, standard recommendation from all competent engine builders - but it also should not be much below that, say 200F. In most cases, oil is overcooled. As it is an easy retrofit, you could leave it off and add later if you do not have one. I would tape a thermocouple probe to the feed pipe to the filter as the best place to measure real oil temp to the bearings. Note that excessive oil pressure leads to heating of the oil beyond the sump temps.

Colyn's approach is the simple best solution. And oil coolers do act as a significant cooling system for the engine on Cooper S it was estimated that over 30% of engine cooling was from the oil, but of course that car had all those gears churning the oil up. There is, however, not necessarily a direct correlation between oil and water temps.

FR Millmore

I hear from an MG LMP675 (MG-Lola EX257) owner that the engine builder (Lola) cringes if the engine oil temperature is not at least 210 before running it to red line in competition, 220 minimum is preferred, and higher temperatures are not much concern. If you start hitting 265-270 because you were running it really hard in warm weather, let it cool down to about 240 before shutting it down. It won't hurt anything. (Not the same as our vintage MG engines of course). Modern engine oil is much better stuff than the straight weight stuff we had in the 50's and 60's. It still thins out some and drops oil pressure a little when hot, but it is not likely to damage either the oil or the engine. If you would run oil temperature above 250 regularly, then you might consider using synthetic oil, which may be good up to 300dF or higher for short periods.

Some modern cars incorporate an engine oil cooler with the engine water cooling system. This not only cools oil effectively, but also helps the oil get up to proper running temperature quicker on cold start and in cold weather, which is a good thing. In essence, oil temperature is being controlled by the same thermostat that controls coolant temperature (especially the desired minimum temperature). When oil is cooled by water, the oil temperature will never be lower than coolant temperature, but oil temperature can be (and usually is) a little higher than coolant temperature. Some modern engine controls will derate engine power when oil temperature goes over 250dF.

When oil is cooled by ambient air it can often be way over-cooled. For cold weather driving you can use a thermostatic bypass valve to allow oil to bypass the oil cooler, or you can install a cover on the oil cooler radiator to stop air flow. You want oil temperature to run above 210dF regularly so it will boil off any condensed water that will be incorporated in the oil at lower temperatures. Keep in mind that water is a byproduct of combustion.
Barney Gaylord

Yes, race engine builders want the oil at some fairly high temperature, because the engine is built with clearances set for those temps, and they cam be maintained. They also change the oil at a couple of hours or max 600 miles (= 3 hours operation) at Daytona.

We are not talking about race engines here. The typical street engine does not even begin to heat the oil significantly until it has been under load for 15 or 20 minutes, and idling or traffic lights/jams do not count, which means many engines never get the oil hot in normal use. It is desirable to get the oil near boiling water temps, to dry out condensate, a most evil stuff. That means 200F+, one excellent reason to run high temp thermostats. But, oil does begin to break down after long periods above 220F, as I said above. It is true that modern oils are more stable, and synthetics even better, but long duration high temps over months kills oil, and that kills engines. 220 has been used as long as I can remember, as the desirable and realistic target figure by many engine builders.

Further, street engines must be clearanced to work from cold to somewhat overheated, over long and/or repeated periods. If you want to preheat your oil from cold, and change oil weekly or daily, go ahead and run it at 270.

FR Millmore

i was able to fit the oil cooler in front of the condenser and radiator but feared it would preheat them so i located the oil cooler beneath,not wanting to cut the car and running a front bumper i installed a thermostatically controlled fan to the cooler but as of now can not use the hand crank and that is an inconvenience

The cooler is an asset if you drive hard and/or have other heat producing accessories. As you intend to drive at some altitude with air conditioning, there is no way I would not run a cooler on your car.

You might want to get a gauge as Barney suggests to monitor temperature and thus experiment with cooler and air conditioner core placemenst if necessary. You can install a pipe thread 'T' fitting where the oil line comes out of the block at the rear of the block to do that.

Anything under 220 F or so is fine. If it gets above 250 F, start worrying, although as pointed out, modern synthetic oils will take it much better than older dino oils.
Bill Spohn

This thread was discussed between 26/08/2012 and 27/08/2012

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