Full Synthetic or Semi?

[simon86]

Due for an oil change on my Honda Civic EK. Previous service i used Penrite 10W-40 semi synthetic. Just wondering if full synthetic is better and whether or not i should use it this time.

Thanks.

[aaronng]

It's up to you and your wallet. As long as you use the correct viscosity, then the oils perform well. Full synthetics have better resistance to high temperature prolonged operation such as on a race track. If on street, you can continue to use semi synthetic and change every 5000-7000km or 6 months.

[tank]

Mineral oil change every 5,000 kms or 6 months.
Semi synthetic oil change every 7,000kms or 6-9 months.
Full synthetic oil change every 10,000kms or 9-12 months.

Thats the maintenance schedule I follow. But for track days and motorkhana, use only fully synthetic oil. Fully synthetic oil will last no more than 3 track days max. Better to change after every 2 track days.

Also, check and top-up engine oil as required.

[dougie_504]

If it's a used motor then go synthetic, but don't use synthetic in a new car/straight after rebuild

[lithium]

It's up to you and your wallet. As long as you use the correct viscosity, then the oils perform well. Full synthetics have better resistance to high temperature prolonged operation such as on a race track. If on street, you can continue to use semi synthetic and change every 5000-7000km or 6 months.

this is good advice :) it's all about the depths of your pockets. generally synthetics are better than semi-synthetics which are better than mineral-based. in this case i believe 'better' means that the oil viscosity remains stable under temperature stress. so generally, synthetic will retain its lubrication qualities for longer than the others. this is why some people recommend longer change intervals for semi/full synthetics.

but look at it from the other way. if you drive the car on the street (disregarding extreme conditions such as trackwork, where a good synthetic might be required due to constant high temperatures and high RPM operation) good oil is all about maximising the life of your engine by decreasing internal wear. if your plan is to keep the car for 3 years and then sell it, is synthetic really needed? it's really up to you

all that said i use synthetic in my car for no better reason other than i like it, and plan to keep it indefinitely :)

[VT3C]

Mineral oil change every 5,000 kms or 6 months.
Semi synthetic oil change every 7,000kms or 6-9 months.
Full synthetic oil change every 10,000kms or 9-12 months..


personally I'd go the opposite of that.. Mineral oil will provide less lubrication but will last longer and better at cold start.. synthetic wont last as long but lubricates better... not sure if that's the best way to describe that though..

easy way to tell - check your oil whatever it is every week or 2 and when it starts to go dark brown / black.. it needs to be changed. any track day should get fresh oil.

As a rule i change synth every 3,000kms if that. semi synth about 5-7,000kms and mineral oil 8-10,000kms.

[xclusive_eg8]

whats a good oil for a d15b7 thats just touching 185xxx??? I used castrol magnatec 10-30w last service (3000km ago), but have been told that the engine is blowing some smoke, so oil or coolant is too blame...

ooo and the car is normally warmed up before being driven, and well its not driven lightly

[lithium]

if the engine is blowing smoke try something thicker. 10w-40 or 15w-40 is good :)

[aaronng]

personally I'd go the opposite of that.. Mineral oil will provide less lubrication but will last longer and better at cold start.. synthetic wont last as long but lubricates better... not sure if that's the best way to describe that though..

easy way to tell - check your oil whatever it is every week or 2 and when it starts to go dark brown / black.. it needs to be changed. any track day should get fresh oil.

As a rule i change synth every 3,000kms if that. semi synth about 5-7,000kms and mineral oil 8-10,000kms.

So far my engine has used both mineral, hydrocracked synthetic and PAO fill synthetic. I consistently found that for the mineral oil, the engine started to operate roughly at the 7000km mark. I had this consistency for 3 oil changes (1.5 years). I switched over the synthetics and had no such roughness issues after the 7000km mark. I've gone up to 10,000km and it is still smooth.

Synthetics should both lubricate better and last longer than a mineral oil because it relies less on viscosity modifiers in the additive package to give that operating viscosity range.

[aaronng]

if the engine is blowing smoke try something thicker. 10w-40 or 15w-40 is good :)

No, the first number is the cold viscosity at -18 ºC. There is no point going for 15w-40 over the 10w-40 because at operating temperature of 80-100 ºC, the viscosity of both oils are around SAE40. If it is blowing blue smoke, replace the PCV valve first. If you are still getting excessive blowby, then you can try masking the problem with a thicker oil. If you go too thick, you end up risking wear to the rotating assemblies in the head (such as the cams), which also relies on the oil for lubrication.

[lithium]

I used castrol magnatec 10-30w last service (3000km ago)


if the engine is blowing smoke try something thicker. 10w-40 or 15w-40 is good :)


No, the first number is the cold viscosity at -18 ºC. There is no point going for 15w-40 over the 10w-40 because at operating temperature of 80-100 ºC, the viscosity of both oils are around SAE40.

i know they are both SAE40 once operating temp is reached however i believe xclusive_eg8 was previous using 30 weight oil
but good post apart from that :)