Oil Question



I’ve had my oil changed several times at an auto repair center but recently found out that they are not putting in the manufacturer’s recommended weight oil. They claimed it was alright to use a partially synthetic oil *5/30w) instead of the recommended 5/20/

Both vehicles are 2003 ford products (f-150 and Taurus) with 63,000 and 86,000 respectfully.

Will this cause me problems in the future,and/ or is this an acceptable practice, even when I advised them that I needed the 5/20.


The 5w30 is a slightly thicker oil that will, if anything, provide better protection than the 5w20. The manufacturers have started using 5w20 because the slightly thinner oil gives slightly less resistance and thus gives slightly better fuel economy. 5w30 has been the standard oil for a long time and I would venture to say that most 5w20 recommended vehicles will be run on 5w30 for much of their lives will no ill-effect.


Frankly it greatly irritates me when I hear of a shop that does not follow the manufacturer’s recommendation maintenance schedule, even in a small way, without first getting the owner’s informed permission. The change they made is not likely to cause problems. However they should have explained what they were doing and why.

I wonder what else they may or may not do without asking you?

Many shops get oil bulk as it is cheaper that way. Not a thing wrong with that, but they are less likely to have as much choice that way.

I drive a car that has some very specific oil requirements. Most cars don’t. But using the wrong oil in my car and the oil you got would almost certainly be wrong for mine, would likely cause me some expensive problems.


turbo sludge?


No damage will be done. Both vehicles allow for the use of 5W30 under most conditions, even though it is not preferred, if I remember correctly. Next time be firm at the front end discussion about exaclty what weight oil you want. Most likely reason to use 5W30 is that is what they have in bulk, and it is cheaper. You may have to pay extra to get 5W20 at the garage, because they may not routinely stock it, and probably not in bulk.

Your choice on “acceptable practice”. I don’t leave any doubt what I want done, and specify a fluid preference if I have one, when I leave my car at a garage.


Most passenger car engines are flexible enough in their lubrication requirements to happily accept multi-visocity oil in various weight ranges. Many Southerners traditionally switch to a higher weight oil in summer, lower weight in winter.The partially synthetic 5W-30 is quite suitable for your vehicles and you should not worry about it any more.

The shop was technically correct in stating that their oil was OK for your vehicles. Clearly this information should have been provided to the customer beforehand. If not then it should have been mentioned on your receipt. Probably it was and you did not notice. Anyway, if this practice still bothers you, switch shops and check beforehand.


Maybe I’ve been asleep too long in my cave, but just what is “partially synthetic” oil? I always thought that synthetic and regular petroleum oils were incompatible.


I think a more correct term is semi-synthetic blend. Many of the major oil brands provide a blend option. Motorcraft’s whole line, as I recall, is now semi-synthetic, or very close to it.


Your vehicles will actually benefit from the 5W30 semi-synthetic (about 50% synthetic) by having longer engine life. The 5W20 is entirely driven by Ford needing to meet the Fuel Economy Standards. A few of these will burn out their engines going through Death Valley in July, but what Ford pays out in warranty will dwarf the CAFE penalties for not meeting the fuel economy standards.

Only the US has fuel economy standards at this time, and a Mazda 3 or Toyota Corolla will have differnt oils recommended in different coutries where these cars are sold. The 2007 Corolla, for instance, should use 5W20 or 0W20 in the US, but uses 5W30 in Canada, a much colder country (without fuel economy standards) on average.

In Malaysia, where the temperature goes from 95F during the day to 75F at night, the Corolla often uses 20W50!!! oil with Toyota’s blessing. It should use 15W40 in that climate for better fuel economy.

Since your cars are out of warranty, use the best oil for the longest life with reasonable fuel economy, and that is normally 5W30 in most of the US. If you live in Florida, a 10W40 would be a good choice. If you live in Alaska, a synthetic 0W30 , such as Mobil 1, would be your best choice.


I’ve heard that from several people…and it’s totally bogus. I’d like to know what source people are reading or hearing this from.

You can mix and match regular dyno oil and synthetic oil til your hearts content. In fact you can by the oil already premixed (synthetic blend)…or do it yourself.


Doc, (without fuel economy standards) Eh? Explain.


I understand at this time, Canada subscribes in principle to the US EPA standards, but they are guidelines only for the manufacturers. In the US there are severe financial penalties for not meeting the Corporate Average Fuel Economy (CAFE)standards.Mercedes paid $60 million fines for not meeting them in 2006.

In the near future, cars in Canada will have to meet a fuel economy standard, but up until the end of 2007, only guidelines were in place. On average cars are smaller in Canada, and fuel economy is higher than in the US.


Agree; EXXON had a low temperature oil called XD-3 0W30, which was 50% synthetic blend. It was a superior truck engine oil for cold weather starts. You can mix mineral and synthetic oil in any proportion you want.


Both the Mocraft and Walmart’s synthetic are probably very good values and are available at Walmart.