Semi or fully Synthetic

[froggy]

Hi, my local " Motor Factor " supplier tells me that I should be using Fully Synthetic oil in my S1 Xantia , not Semi ! according to Citroen ! any advice anyone, cheers Terry.

[xf1ref]

Synthetic oil mantains its properties a longer time than semi and has a grater temperature resistance. Semi is a mixture of synthetic and mineral oil.
For xantia s1 is good semi or fully. At my s2 I used both but with no difference.
I use 5w40 even the car have 180k km and no oil consumption.

[c.morewood]

I always use fully syntetic.
I have a BMW K100 motorcyle which used the standard 20W50 for the first 30K miles then semi for the next 70K.
I replaced the camchain and guides at 100K and the guides were almost worn through. I was also having a problem starting in the minus temperature conditions.
I decided to try using a thinner fully synthetic oil from that point and never went back to anything else since in all my vehicles.
The BM's cold starting improved as the oil allowed the starter to spin faster. I have another 230K on the cam chain guides and they look like new and the inside of the engine has cleaned up from a mucky brown colour to a light see through tan... the oil sight glass never needs replacing now whereas it needed replacing due to its brown opacity every 15K.
I now use Mobil1 0w40 in the car from Costco £27.



Meant to say I changed the oil every 15k on the bike with a filter change every 5K (the service interval)
I Change the oil filter every 6K on the car and oil every 12500.

[Peter.N.]

If you change it regularly semi synth is fine and much cheaper, I pay about £13.00 for mine at Trago Mills.

Peter

[Old-Guy]

Interesting. I think the XUD engine predates the introduction of (semi-) synthetic oils. IIRC the handbook specifies 15W40 and (translating from the various standards) a good quality normal detergency diesel mineral oil. This is no longer available. Fully synthetic is way over-specified, semi-synthetic 10W40 diesel oil is the nearest available. I too agree that the best way to protect these engines is to use a good semi-synthetic and change it every 5-6,000 miles.

Of course, a more modern engine developed to exploit fully synthetic oil should be filled with it and changing it more frequently than specified can only help prolong the engine, especially if the vehicle is used for short trips.

[myglaren]

Hah
I just discovered in one of the many hidey holes here a new 5L of 15w40 mineral oil and wondered what it was for.
Must have been bought for my son's 306 and never used.

[lexi]

I am impressed with the motorbike mileage.......flippin amazing!