Mechanic used thick oil

Joined
Jul 20, 2025
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3
Location
Western Australia
Greetings from Australia. I'm new to the forum.

I recently bought a 2014 Honda CRV 2.0L Petrol. (R20 engine). I've checked through the service records and discovered that the previous owners mechanic has been using 10W-40 oil. The manual states that this engine should run 0W-20 or 5W-20.

I plan to do my own servicing going forwards and wondering if I should change back to the recommended stuff or keep using the 10W-40. It's only got 105,000km (65,000 miles).

I often hear advice about using thicker oils with older engines but can one go back to thinner oils? Where I am, it never gets below freezing in winter and in summer it's not uncommon to get 40C+ for weeks at a time.
 
You can use up to 20w-50 in the owners manual I believe
Running a 20W-50 in THAT ENGINE is something better KNOWN than 'believed in'.

Don't get me wrong, 20W-50 is found on many oil spec charts...it just helps to be dead certain for each application.

A friend's 1985 Subaru (1.7l) called for 20W-50. For funzies, I used 20W-50 in my 1976 Chevy Nova 250 (straight six) and all the engine did was click a lot, so I restored the usual oil.
 
Greetings from Australia. I'm new to the forum.

I recently bought a 2014 Honda CRV 2.0L Petrol. (R20 engine). I've checked through the service records and discovered that the previous owners mechanic has been using 10W-40 oil. The manual states that this engine should run 0W-20 or 5W-20.

I plan to do my own servicing going forwards and wondering if I should change back to the recommended stuff or keep using the 10W-40. It's only got 105,000km (65,000 miles).

I often hear advice about using thicker oils with older engines but can one go back to thinner oils? Where I am, it never gets below freezing in winter and in summer it's not uncommon to get 40C+ for weeks at a time.
Never gets below freezing you could probably run a straight 30wt and be done with it.
It never gets below freezing and weeks of 40c sounds like you wouldn't want 20wt oil in your engine at all.
It get almost 40c where I am but also tries for -10c so I use 5w-30 and 10w-30 in all my liquid cooled engines.
 
10W-40 isn’t very common anymore here in NA.
But in Auz, it is still a very common grade; so ‘most’ of your modern 10W-40’s are probably syn-blends, like 5W-30 is over here. An example would be Castrol Magnatec 10W-40.
So, on a fuel-diluting Honda, a quality 10W-40 would be a great oil to use.
 
Thanks all for your helpful insights. From what I have read so far, oil viscosity doesn't matter that much.

All of my previous cars have required 5w-30, I've still got a full bottle of this stuff in the garage and will used it for the next service.
1000000276.webp
 
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