Engine Oil

[Gentlegiant]

I have an old Ford Focus. The Halfords website says that I should use 5W/30 engine oil. However, I have half a can of 10W/40 in my garage, which I am fairly sure I have used with this car in the past. Would it be inadvisable to just use up the remaining part of the 10W/40?

 

[Mottie]

Yeah, use the 10w 40, it won’t hurt an old motor. A 50/50 mix and you’ll end up with 7.5w 35!

 

[JohnD]

I have an old Ford Focus.

You don't say what year or engine it is, but there is quite a good chance that, if you could find the manufacturer's handbook, 10/40 will be among the recommendations the makers laid down at the time the engine was designed.
https://www.ford.co.uk/owner/my-vehicle/download-your-manual

It's likely that any modern oil you are able to buy today will be superior to those on the market when the engine was first built.
I believe they've been on the market for over 20 years.

Much more important is fresh, uncontaminated oil and unclogged filter by keeping the changes on schedule.

 

[Stivino]

When I'm in doubt I usually go here.

 

[JohnD]

If you do maintenance checks yourself, it's worth looking up makers recommendations for oil, antifreeze, tyre pressure and so on and printing them off. I usually keep a litre bottle in the boot. Oil companies will try to guide you to their more expensive products.

I found this page on a 2005 Ford Focus manual, though yours may differ....

ENGINE OIL
Engine oil change
Ford/Motorcraft Formula E
SAE 5W-30 engine oil.
Alternative engine oils with the
viscosity SAE 5W-30 meeting the
requirements of Ford Specification
WSS-M2C913-B may also be used.

Engine oil top-up
If you are unable to find an oil that
meets this specification, you must
use an oil of the viscosity
SAE 5W-30, SAE 5W-40 or
SAE 10W-40, according to ambient
temperatures, meeting the
requirements of either
ACEA A1/B1 or ACEA A3/B3
specifications. Use of these oils
may result in longer cranking
periods, reduced engine
performance, reduced fuel
economy, and increased emission
levels.

Engine oil spec WSS-M2C913-B was also formerly recommended for some Jags, and has since been superceded by '913-C which is compatible. If your car is old you can get a cheaper own-brand such as Halfords or Carlube that meets the spec. "Edge" is one of the most expensive.

 

[DIYspanner]

May I suggest Millers Oil checker which seems to be the most comprehensive oil adviser.

How old is the oil you have in store?

 

[sxturbo]

5w30 is only recomended,

the weight of the oil can be altered at your discretion depending on the external ambient temperatures, it will be listed in your manual what viscosities cover what range.

the important bit is to ensure the oil "spec" is correct, as out of spec oil "can" wear an engine prematurely. (this is specifically so on VW PD diesel engines, use the wrong oil and the cams and followers eat themselves)

in the UK 10w40 is perfectly adequate for all temperature conditions we see.

the thinner oil aids with fuel consumption and emission requirements set by eu/uk or wherever the cars are sold.

all that being said, the ford focus engines dont have any special technology in them (unless you car is diesel and has a dpf) and so switching oil will cause you absolutely no problems what so ever.

 

[DIYspanner]

The Ford 5w30 oil which carries the Ford WSS-M2C913-D is backwards compatible to the earlier WSS-M2C913 A thro C.

Mannol blend a 7707 OEM with higher viscosities compared to other 5w30 WSS-M2C913-D oils.

For 40° and 100°, most 5w30 WSS-M2C913-D oils are around 55cSt/10cSt whereas 7707 OEM is 63.4cSt/11.4cSt, a rather thicker blend. Rather weird!

Of the VW PD specs, 505.01, 506.01 and 507.00, we ran a 1.3 Ford KA on 5w30 507.00 for a year no bother at all.

 

[Burnerman]

Old timers (me) recall when the first Ford Zetec 16v engine came out in the M reg Escort.......
The oil that Ford initially specified caused the valves to stick in the guides, so the viscosity and spec of the oil was changed to a much thinner grade. The valve guides were modified too.
People I knew at Pattersons Ford Newcastle roped me in to change cylinder heads.....must have cost Ford a fortune.
John

 

[Mottie]

I know there’s dozens of different oil specs, even of the same viscosity but come on, hand on heart, who has ever heard of an engine or a cat or a dpf being ****ed by someone using the wrong oil? I cant remember it happening and I’ve been in the trade for more than 45 years.

Put your reg number in the Halfords site (others sites are available) and see how many different oil spec and grades are shown for it. If it was that critical, they’d spend most of their time in court. For my Evoque, they list semi synthetic, fully synthetic, 5/30, 0/30 A5, C1, C3 and a few more. It ain’t that critical.

 

[sxturbo]

I know there’s dozens of different oil specs, even of the same viscosity but come on, hand on heart, who has ever heard of an engine or a cat or a dpf being ****ed by someone using the wrong oil? I cant remember it happening and I’ve been in the trade for more than 45 years.

Put your reg number in the Halfords site (others sites are available) and see how many different oil spec and grades are shown for it. If it was that critical, they’d spend most of their time in court. For my Evoque, they list semi synthetic, fully synthetic, 5/30, 0/30 A5, C1, C3 and a few more. It ain’t that critical.

I agree it is quite rediculous and could be whittled down to just a handful of oil grades if all the manufacturer worked together, however it does make a difference, you may not see it in the motor trade, you probably just see "another car" with a blocked dpf and not pick up that it's caused by an incorrect oil being used.

It takes a few thousand miles so you wouldnt realise.

However when researching and developing where all the components are run using various types of oil and dismantled and inspected at pre determined intervals, there is a difference.

the manufacturer designs the engine they are mostly interested in making it last long enough for the warranty to expire, and the oil will be part of this.

Modern engines are designed to burn more oil than previous generations (sounds a bit backwards) but it's done to reduce friction and increase mileage and emissions, this is where the oil specs really work.

 

[JohnD]

Mannol blend a 7707 OEM

My car has the correct grade embossed on the filler cap as a reminder, so I always insist on "710"

 

[Keithmac]

They run thin oil to eek more mpg out of the engines, the oil is more than likely worse in regards engine wear etc but mpg is king when selling cars..

 

[Stivino]

They run thin oil to eek more mpg out of the engines, the oil is more than likely worse in regards engine wear etc but mpg is king when selling cars..

It's not only about fuel consumption. Thinner oils started to be used more when engines became taller, i.e. the more common use of OHC engines.
It was difficult to pump a cold thick oil to the top of these engines on initial start up, therefore, a lot of them suffered premature camshaft failure. In order to get the oil to the top of the engine on start up the oil used became thinner.
Back in the day with OHV engines, think Ford Escort, Vauxhall Viva, Hillman Hunter, Avenger etc, all these cars had OHV engines and 20/50 went into everything without a second thought.

 

[DIYspanner]

If an engine spec says 5w30, I'd put a VW504.00/507.00 oil in. We even have an i20 petrol running on it.