Thanks for that, I'm really confused now
last week I was all set to use 10w-40 Semi synthetic after reading everyone's replies.
I was given a gallon of 5w-40 a few weeks ago which I was about to give away, and Shell say it's Ok to use it.
Any chance I can use Olive oil, extra virgin of course
I know mate, what a pain in the @$$.
For mixing I don't think the issue is with the 5w over the 10w but moreso the synthetic v semi-synthetic. Different brands have different chemical formulae for the synthetic aspect.
To confuse you even more I would try & be consistant. So...if you have 10w40 in the F-engine use 10w40 to top up as decided earlier. But when you get an oil change make sure it is a brand that you can readily buy off the shelf (unlike AGIP - which is a really good oil, but not widely available in the UK).
If you want to find a home for that gallon of 5w40 Helix you could...
a) Flog it to Boxer for a packet of fags
(that is cigarettes for those of you who speak American
b) Fork out for another gallon of the Helix + an oil filter and do an oil change. But then be prepared to get another litre to do your top-up as & when. AND stick to the plan for the life.
c) Use the Helix in one of your other motors when you get an oil change and then forget about it.
d) Give it away as a present to someone else along with the dilemma
My choice a, c or d. Given the climate in the UK, I reckon you are fine with the 10w40 SemiSynth both performance & price wise (if in doubt look up Shell's profits!). If the global warming means we start to freeze our knackers in Summer and sweat in Winter then go with the 5w40/5w50 ala Dennis.