question Which engine oil for a AEC?

[Mattyboy]

Need some help please, I have an AEC Matador with a 7.7 diesel engine, it's not a bad engine oil pressure when hot is ok and it doesn't leak out of every joint on the engine.

When I changed the oil last time I was told to use an old fashioned straight 30 non detergent oil for various reasons. But when the engine gets hot it gets far to thin, the upside of this oil is when I removed the rocker covers it has removed all the sludge from the top of the engine. The oil has only done about 500 miles (2 years) and I think I'd like to change it, but what do I use? I phoned Witham's the oil 'expert's and when their computer couldn't find 'AEC' they couldn't help!

 

cheers chaps

[Redmat]

The Matador maintenance manual specifies 30 H.D. which is, as far as I have been able to find out, what you are currently using. Mine runs on a similar product without any problems. Beware of high detergent oils which can dislodge or dissolve accumulated deposits in an old engine which then have the potential to block oilways etc. with disasterous results.

[Ed Batchelor]

I use Morris straight 30 weight oil in my Matador which is as far as I can tell correct specification and I've had no problems.

[matador]

See AEC Forum.

 

Must be straight mono grade mineral engine oil as no full flow filter fitted, just pick up strainer.

 

NOTE ALSO

 

gear oil must be non EP.

[16svt]

Can I ask what oil pressure you are all getting? I get 60 psi cold idol, 35 hot (after working hard) full revs and 12 hot idol. I think this is very low myself. but a few others that have had Matadors for years tell me not to worry about it. Any thought?

[Mattyboy]

that's cheered be up, I did a very long drive yesterday and my oil pressure dropped to about 15psi hot tick over and the thought did cross my mind. you can increase the oil pressure by adjusting the pump with the screw on the sump (this is something I have not tried) my question to you and other matador owners is, when yours is hot and you stick your head under the front of the sump can you hear your oil pump rattling away? or am I worrying again? I am still think about changing to a multi-grade, straight 30 just gets to thin when it is hot.

 

If it makes you feel happier I have a spare engine in my yard that runs at zero oil pressure at tick over and it was run in a matador for years and years!

[Degsy]

I wouldn't like to use a multigrade oil in an old engine unless the engine was as new or rebuilt as the detergent properties just would not be compatible with an old engine. These old engines were designed to utilise monograde oils of a far lower quality than the oil available today from manufacturers such as Morris Oils who make lubricants specifically for vehicles such as the Matador. When you say you are using a straight 30 grade is it designed to be used in old diesels or is it just a cheap utilitarian oil. Another point to remember is that service intervals were much more frequent 60 plus years ago, commonly oil changes occurred every 1000 miles and a lot of engines would be rebored every 10,000 miles. I am of course generalising so you would need to consult the Matador manual for recommended service intervals. A friend of mine has run Matadors since the sixties and I will ask for his advice when I next see him and pass it on to you.

[philb]

When I bought my Matador the oil pressure was very much Like 16svt quoted but probably a bit lower still when idling hot - and that was running straight SAE40. Cutting the story short, when I stripped the engine I found the main bearings were seriously worn - the centre main had about 40thou clearance (ten times what it is supposed to be). The end bearings were a bit better so, presumably, the crankshaft was flexing in operation. Reassuringly the big ends are largely protected from abrasives by the centrifuge action of the the hollow crank-pins with lateral exit ports (nice design feature). Anyway, having rebuilt the engine it now holds 50psi hot running and about 30psi hot idle, on SAE30 - much happier.

 

Various comments on what has been said so far:

 

Adjusting the pressure relief valve spring probably wont help the pressure when it's hot (unless, by fluke, the valve is leaky)

 

Detergent won't hurt as long as the engine is fairly clean to start with but it could cause trouble if there is a lot of crud to break loose and circulate.

 

Dispersant is the devil. That causes the abrasive crud to stay in suspension and circulate for ever rather than drop to the floor of the sump. OK if you have a full flow filter - but we don't.

 

Multi-grades are OK in principle but they will probably result in high ash deposits in the ring grooves (because of the high level of oil consumption by design - compared with modern engines) and I don't know of any multi-grades that do not also have high levels of detergent and dispersant.

 

So, back where we started, straight SAE30, changed frequently. Because there are very few additives to lose their properties, cheap is probably as good as expensive, not that I've seen much price variation.

 

Ducking for cover.....

[Degsy]

philb, the only thing I would disagree on is oil quality. We regularly get vans in our yard offering oil from some company I've never heard of, when told where to put it the price is reduced to ridiculously low levels. The suppliers are not oil companies but merely packers and there is no real knowing what's in the container. I've seen the same sort of thing in accessory shops but having seen the results of poor quality oil I wouldn't use the stuff on pram wheels.

[Tony B]

PhilB, I've got Halford's semi synthtic 20/50 in my Dodge WC51. That is good stuff and keeps higher pressure after a long run than my previous Valvoline straight mineral 20/50. My new WC54, is running on Straight 30 , pressure from certain respected members here, . So far she hasn't had a long run on fresh oil so I can't compare, but a recent 88 mile run home from Portsmouth, on oil God alone knows how old. Pressure stayed a steady 55 lbs all the way through. I have now flushed the engine out and changed oil and filter There was nothing nasty in the mix, apart from the colour. The one thing I would say is a motto painted on the wall of the enginnering shop at college, 'Good oil and greas are cheaper than repairs'.

[N.O.S.]

With Matadors, the best oil is either black or 'oil'-coloured - if it is any shade of metallic (silver or aluminium) you've got problems :cool2:

[philb]

Degsy, I agree, when I said cheap I wasn't thinking of VERY cheap unbranded stuff. Tony, with the benefit of a fine filter you are free to choose. I don't suppose any of use do enough mileage to get into the coking, sticking ring problems. Without a filter I think it's best to let the crud settle.