It’s an age old debate for car enthusiasts. How often should you change your oil? And if you do so regularly, is it worth paying the extra for apparently higher quality oils? Well, I hope to answer that with my own experiences.
A long time ago, I ran an old MGB and I had head gasket problems. BTW, if you want to learn how to repair cars and do your own maintenance, I thoroughly recommend buying an old british car and attempting to run it day to day. Preferably from the ’70s. I guarantee you’ll be pretty handy with a spanner in less than 6 months… 😉 Anyway, I’m straying off the point here, so:
I decided to change the head gasket myself. Took me all weekend, but I had to get it done, because it was my only transport and I was staying at my brother’s place over 200 miles from home. As I was doing it, I noticed how coked up with carbon the engine was, and I tried scraping some of it off, but it seemed like a crappy job so I left it. I also misread the manual I was using and torqued the head nuts up far too tight, snapping one of the studs in the process. This was not good, as it meant the head gasket went again a week or 2 later.
Not to be out done by the old beast, I decided to replace the stud and fit a competition head gasket, thinking this should solve the problem. As a treat for it, and to try to coax it into being more reliable, I filled it up with some pricey Mobil 1 as well.
But no. The gasket went again. Apparently the competition gaskets aren’t the most reliable because being of metal sandwich construction, you have to make absolutely sure the block deck and head face are completely flat, i.e. recently skimmed, before you fit them. Naturally, not having my own machine shop, this wasn’t the case and it leaked. So back to the gasket shop I went, where an old racer told me, most people who race ‘B’s still use the standard gasket for this reason. Doh!
Anyways, it was “Off with her head!” again, and I saw something strange. After relatively few miles, the Mobil 1 had completely de-coked and cleaned the inside of the engine!
Since then, I have tried this on a number of old cars with some success. However, there is a small caveat. The latest old nag I have tried this on is a renault laguna turbo diesel, with 110,000 miles on the clock. When I first got it a few weeks ago, it seemed very sluggish, but then my previous daily transport had been a V6.
At 100,000 miles I thought it was probably a bit coked up, and judging by the crappy re-molds it was fitted with, surely not serviced as well as it should have been in later life, so in went the mobil 1, and out came the old oil. This was unbelievably dirty and even had some sediment in it. Yuk!
Results? Good and bad.
The Good: The turbo now spools up more quickly and at a good 500 rpm lower down the rev range too, and the engine is certainly smoother.
The Bad: Big blue clouds of oil smoke on start up.
Why though? Well, the mobil 1 has obviously shifted a lot of crap out of the oil system, including the turbo, so it should prolong the life of that part. Unfortunately, it seems the valve guides are quite worn, which is to be expected after that sort of mileage, so the muck and sludge must have sealed them against drawing oil into the cylinders. Now this has been removed, the car smokes.
Wonder if I can sludge it up again before the next MoT test…
9th May 2012 – Quick update. The car has now stopped belching large quantities of smoke on start up. Not sure why this is, perhaps the crap has just moved around a bit I don’t know. I have also started running the vehicle on a mixture of diesel and cooking oil so maybe this is a factor. Well we’ll see when I next change the oil again. As mentioned, the last lot was full of all sorts.