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99 1.8 Confusion over acceptable oil grade to use? - jp147
In my Ford Focus (UK) petrol owner's guide it says that 5w30 engine oil should be used at all times for optimum performance. However, further down the page below where it says engine oil top-up it says that 5w30, 10w40 or 5w40 oil can be used albeit with reduced fuel economy, performance etc. Does Ford mean that e.g. 10w40 can be used for a complete oil change (as it says "top-up" it doesn't say by what amount e.g. 1 litre or more) or only for topping up. Even more confusing, the Hayne's manual for this model says that 5w30, 10w40 or 5w40 can be used but higher viscosities e.g. 15w40 could cause damage. I have read in the car mechanics magazine that the use of higher viscositites than 5w30 can cause valve or other problems later on.

So I would like to know once and for all whether 10w40 oil would cause damage to the engine


Edited by Dynamic Dave on 06/03/2009 at 18:28

Tags: technical issues oil maintenance and servicing oil changes damage

99 1.8 Confusion over acceptable oil grade to use? - TurboD
reading my mondy 2l handbook, I understand this to mean you can top up if the correct oil is unavialable. which is 5/30. I know a colleague who has run into engine problems by using thick oil- for older cars- rather than the correct stuff on his Ford.
You are well out of warranty so it is on your head what happpens to the engine, but within warrantly I stick to Ford 5/30
99 1.8 Confusion over acceptable oil grade to use? - Number_Cruncher
>>once and for all whether 10w40 oil would cause damage to the engine

Once and for all - NO a million times, NO! Your engine, if damaged, was not damaged by using 10W40 oil.

Edited by Number_Cruncher on 06/03/2009 at 19:35

1999 1.8 Ford Focus petrol engine oil grade questi - jp147
This question refers to the UK Ford zetec E engine (1.8 and 2.0 l).

I know that Ford recommend that only 5w 30 oil is used in all the zetec engines (zetec SE and zetec E) and I fully agree that only this grade is ever used. However, if during a service a mechanic put in 10w 40 instead of 5w 30 and the owner, unaware of this mistake, drove the car for 3 or 4 months covering say 2000 miles, what if any damage would occur and also if the owner then (after 3-4months) became suspicious because of reduced fuel economy decided to change the oil and made sure this time it was definitely 5w 30 that went in, would any more damage be caused to the engine or is it the case that damage (if any) is only done whilst the 10w 40 oil was in the engine ?

I have read conflicting stories on the internet that it doesn't do any damage and others that say it causes premature wear, valve/tappet problems and blocked oilways in the lubrication system.


Moved to one of your many many previous posts where you have asked similar questions. Just *maybe* you'll see the reply telling you that your engine WAS NOT damaged by the wrong grade oil being used!!

Edited by Webmaster on 13/03/2009 at 23:38

1999 1.8 Ford Focus petrol engine oil grade questi - Woodspeed
Ford started to recomend a high quality thinner oil some years ago, as there was a problem with cheaper quality oil on gently driven cars coking up small oilways and valves. At around the same time newer engines from many manufacturers tightened up engineering tolerances to use 0/30 or 5/30 oil which would result in a very small percentage improvement in fuel economy. I have 2 Ford cars in the family and after 70k miles oil consumption increased. As being thinner it would pass the rings and burn off. So these are now using a 5/40 fully synthetic, which has helped consumption and fuel consumption is not noticeably different. I can not think any "damage" has been done as such. A 5/40 would have been a better bet (flows better at VERY cold temps) and usually that grade is fully synthetic.
Although fully synthetic is more expensive, I push oil changes to 15k-20k (all "home" service) with little worrying top up, and most vehicles have run to or past 200k miles without issue. I know several people who run Mercs, Fords and Vauxhall who report increased consumption around 70k-80k miles using 0/30 or 5/30 who switch to 5/40 and problem solved.
Very good article on oil quality and grades on Honest John front page:

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