Mixing Oils!!!

Post by **ani** » Thu Jun 18, 2009 5:38 pm

I've just topped up the 1279 MG Miget engine with 20/50 multigrade oil. I've no discovered from the service history that it had 15/40 semi synthetic oil in. Can that cause a problem?

Engine is sounding a little bit tractor like but may be unrelated. I'm going to replace the air filter tomorrow to see if that makes a difference.

Post by **PSL184** » Thu Jun 18, 2009 6:36 pm

A old Midget engine should really have 20/50 in it anyway. It probably sounds like a tractor due to the 15/40 ss which is a waste of money on an old engine! Use Asda or Morrisons 20/50 and change it along with the filter every 3000 miles if you only do short runs or 6000 miles if you do more longer runs.....

Post by **dalebrignall** » Thu Jun 18, 2009 6:49 pm

i agree with psl,put 20/50 in there.if its noisy some stp the red bottle might make it a bit quieter.

Post by **ani** » Thu Jun 18, 2009 7:00 pm

stp - wots that??

Post by **PSL184** » Thu Jun 18, 2009 7:15 pm

ani wrote:stp - wots that??

A very thick oil additive - a bit like treacle ;-)

Post by **ani** » Thu Jun 18, 2009 7:30 pm

Makes it sweet then

Post by **bmcecosse** » Thu Jun 18, 2009 7:34 pm

You won't have done any harm - just leave it - but in future use the 20W50. I use ASDA - it's up to you what you use! Someone posted recently that their consumption was much less when using a 'branded' 20W50 - but i suspect it was the completely different use of the car (long runs!) which made the difference. Don't add any additives - waste of cash.

linearaudio · Post by **linearaudio** » Thu Jun 18, 2009 8:49 pm

I was topping up with 10-40 for a whle. When I did an oil change I reverted to 20-50 and subsequently have found a noticeable improvement in the oil consumption, and quieter running.

Post by **bmcecosse** » Thu Jun 18, 2009 9:35 pm

Oh yes - 10/40 to 20/50 will show a change. However - the thinner (less viscous) oil does give better fuel economy - my Vauxhall is specified with 0W/30 oil! And it uses NONE.

Post by **PSL184** » Thu Jun 18, 2009 11:31 pm

^^^ Because the engine was designed and manufactured with tighter tolerances than a Minor could ever dream of.....

Post by **bmcecosse** » Fri Jun 19, 2009 9:04 am

Of course - mainly improvements in cylinder wall finish and piston ring design.

Post by **Stubee** » Sat Jun 20, 2009 6:20 pm

Just to add a bit more fuel to this topic! I would avoid mixing grades if possible as it could affect the performance of the oil but then I'm sure on a normally driven A-series it wouldn't be a problem. As to non API spec oils, I would possibly use them on an engine of unknown history or one which had very high oil consumption but there's no way I'll use some in my recon engine, decent oil for me when you think of yhe job and conditions it endures! I'm thinking of using 15W/40 at the next change, this should be ok on a new engine? I'm sure the latest BL cars with the A series had this recommendation in the late 80's/90's anyway?

Post by **bmcecosse** » Sat Jun 20, 2009 6:41 pm

When I use 40 grade oil - the oil pressure is 10 psi lower than with 50 grade. Still ~ 60 psi (the relief valve is slightly packed) but I prefer to see 70 psi!

Post by **ani** » Sat Jun 20, 2009 6:43 pm

I didn't mix them on purpose

However I've just got a gallon of 20/50 for £6 from Asda (tks BMC) I'm not going to change it fr now as the dip-stick is showing the oil to be really clean. So I'll just top up with 20/50 till it needs it's next oil change

Simples