Urghhh! Noob mistake, added 1 ltr of wrong oil to MK5 Golf - Car has to work harder now

DJMK4 · 28 Mar 2011 at 18:40

Bit of a noob mistake by myself, I read wrong and used 5w40 instead of 5w30, since then, I dont know if another issue has come along at exactly the same time, but the car is having to work much harder when driving and its effecting mpg, even when your cruising on the m'way you have to keep touching the throttle as if you let go your speed will drop at a faster rate than normal.

Clutch down so I am "cruising" makes no difference, still the same speed rate drop.

Is this the oil do you think? If it is, I am going to get a 5ltr and a filter and do an oil change on the weekend.

DJMK4 · 28 Mar 2011 at 18:41

Forgot to mention its a diesel engine

Sin_Chase · 28 Mar 2011 at 18:42

I very much doubt adding 1 ltr of oil to what would be another 4-5L or so would affect resistance inside the engine to have a noticable effect on MPG/the power you need to apply for the same output.

-westy- · 28 Mar 2011 at 18:43

The change in hot viscosity rating shouldn't affect an engine like that, especially as its only a litre.

sigma · 28 Mar 2011 at 18:45

Change it anyway.

DJMK4 · 28 Mar 2011 at 18:46

There is another factor which I need to look at, which are my rear pads, however they still have enough life on them, one of the disks is slightly uneven though, very slightly. Unusually with brakes I can hear noise along with braking if its an issue, I have had no warning sensors yet.

I am more concerned that this only come on since I stuck the oil in

DJMK4 · 28 Mar 2011 at 18:47

sigma said:
Change it anyway.

I think I might just do this

Kenai · 28 Mar 2011 at 18:57

I don't see how the engine could be blamed if you are seeing unusually rapid speed loss even with the clutch depressed.

Seems more likely that the brakes or handbrake or something have become stuck on slightly, something along those lines.

-westy- · 28 Mar 2011 at 19:05

Kenai said:
I don't see how the engine could be blamed if you are seeing unusually rapid speed loss even with the clutch depressed.

Seems more likely that the brakes or handbrake or something have become stuck on slightly, something along those lines.

Agreed - if you're still seeing the same deceleration with the clutch down, that completely rules out the engine, as its effectively disconnected from the road wheels.

DJMK4 · 28 Mar 2011 at 19:11

I'll have a closer look at the brakes over the weekend I think

Fr0dders · 28 Mar 2011 at 19:24

placebo

the difference between 5W30 and 5W40 wouldnt have the effects you describe.

Matt82 · 28 Mar 2011 at 21:43

might make the revs drop faster but i wouldnt bet money on it

Dureth · 28 Mar 2011 at 22:19

You would never be able to tell the difference between the two oil viscosities. Heck even moving to a 0w oil in a race bike engine (revving to 16K rpm) you are only looking at most a 0.5-1hp advantage due to less pumping loses. At lower revs you'll notice no difference at all.

On the other hand I'd be checking my brakes carefully as it sounds like they're sticking.