I know this subject has been discussed in great and excellent detail but perhaps someone could answer a simple question.
My car's manufacturer recommends 10w40 oil but 5w40 can be used when the weather is colder. I have some 15w40. Could I use that or would become unsuitable when the weather becomes colder?
Please visit the Club's website https://www.dloc.org.uk/ to join. Visit https://www.dloc.org.uk/adhoc to DONATE towards the cost of the forum.
Please don't post someone's email address to avoid it being harvested by spambots and it's against GDPR regulations.
Always look at "ACTIVE TOPICS" to see all posts in date & time order as they are sometimes moved; or look at "Your Posts".
Please add Reg. nrs. when posting a photo or anything about a car as this will help searches. Don't add punctuation next to nr. as this negates search.
CHANGED YOUR EMAIL ADDRESS since registering?, click your username and check your address in User Control Panel, Profile, Account Settings.
If you want help to register, use "contact us" at page bottom for help.
Please don't post someone's email address to avoid it being harvested by spambots and it's against GDPR regulations.
Always look at "ACTIVE TOPICS" to see all posts in date & time order as they are sometimes moved; or look at "Your Posts".
Please add Reg. nrs. when posting a photo or anything about a car as this will help searches. Don't add punctuation next to nr. as this negates search.
CHANGED YOUR EMAIL ADDRESS since registering?, click your username and check your address in User Control Panel, Profile, Account Settings.
If you want help to register, use "contact us" at page bottom for help.
Which oil?
-
- Wise Man
- Posts: 847
- Joined: Sat Feb 13, 2016 1:25 pm
- Location: Worcestershire Herefordshire border
Re: Which oil?
A quick scan of the internet would suggest that a 15/40 (mineral) would be suitable for -20C and a 15/40 (semi synthetic) would be suitable for -20C. The quality certification (the letters after the viscosity rating) is also important and should match the manufacturers specifications. I'm not an expert but others on here are
Andy
1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster
1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster
Re: Which oil?
When hot, all of those oils are the same as they are all -40 grade.
When cold all oils are too thick to flow as quickly as they should. Even a 0W oil is too thick. A 0W rated oil will flow more quickly on cold engine startup that a 10W or a 15W.
Changing from a 10W to a 15W merely means the oil takes a bit longer to get flowing until it gets hot. Using a 5W means it will get flowing a bit more quickly than a 10W.
When cold all oils are too thick to flow as quickly as they should. Even a 0W oil is too thick. A 0W rated oil will flow more quickly on cold engine startup that a 10W or a 15W.
Changing from a 10W to a 15W merely means the oil takes a bit longer to get flowing until it gets hot. Using a 5W means it will get flowing a bit more quickly than a 10W.