Mixing Different Grades Of Engine Oil For Topping Up

[paddyk]

Will it be OK to use 10/40 mineral oil if (it is a decent make) to top up a ford endura 1.3 petrol engine which has 5/30 semi synth in it which is what the handbook says to use, The car has done around 80,000 miles and I think it will be OK but I thought I'd check on here, I have googled this but get conflicting answers from various websites. The owner is a friend and I have a new can of 10/40 that I was going to give him as I don't need it but can he mix it with what is in already without doing any damage. just trying to save him a bit of money reallyl
TIA

[DTCwordfan]

Are they different brands as mixing those can cause issues with the different additive chemistry. Tell me which brands you are thinking about....

[paddyk]

Hi DTC. The 10/40 Mineral oil I have spare is Carlube. Not sure what's in friend's car but not an expensive one. Forgot to mention that his car burns a lot of oil (2 or 3 pints a month ??) but the old design ford OHC engines tend to do that don't they when they get a few miles on ? If he could use it might help him out a bit

[DTCwordfan]

He's crazy to use a semi-syn then as yes this does happen and a 5W30 is going to be too thin and risks seepage from his lub seal on his sump. Better to move to a 15W40 such as Shell Helix or Castrol, however the 10W40 will be fine - if its one of Carlubes semi syns, then the grade will be fine and the engine should sound less 'tappety' (smoother).

Carlube is cheap and cheerful. I'm not sure who their additives come from but I have a suggestion from their MSDS it may be Ethyl and that should be reasonably okay. If it's Texaco or Chevron your mate has been using, or even Valvoline, I would be careful as this is where you may get your chemistry problem, Oronite (the add co they use being based on salicylates.).

However, my advice would be to do a full lub change, a new filter and go for a Helix (not that I am biased) or Castrol, the quality does matter and actually impacts on fuel consumption.

One other one, just checl that the lubricants are not diesel based (look for the reference that may read something like SI to SN (the S being the petrol spec) and CF to CI-4 the diesel spec - if it has both that's fine, if only the one then you need the S...... S means spark ignition, C means compression engine.

Change out should be 12-15000 miles on Helix 15W40, depending on how hilly your countryside is or once a year to be sure. He shouldn't be going through litres of the stuff, just the occasional small top up once a quarter or six months.

[ToraToraTora]

yep do what DTC says, change the lot to 10/40 and change the filter.

[paddyk]

Oops - there is a mistake in my 2nd post - should say OHV engine not overhead cam - was rushing too much. It's these pushrod type engines that tend to burn a lot of oil so I believe.

[Msdsonline]

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