When we noticed that oil consumption was getting a little high with the high milage on our van my dad decided to start using Castrol Syntec Blend 15w40 in the aerostar and also in his Plymouth. Both call for either 5w30 or 10w30 in the owners manual...

My question is this.. is it going to harm the engine if we continue to run this oil? If not why does the book say not to use any other type of oil besides 5w30 or 10w30?

I have never really been clear on the effects of using different types of oil in an engine, so if someone would clarify this for me I would be ever so happy...

I would be more comfortable using say Valvoline MaxLife 10w30 in both of them rather than running 15w40.... Especially in the winter time.... but he will not switch the oil unless he has a reason to...


Thanks,
-Mike-

 

I have read articles about oil viscosities. On older vehicles it should not hurt it to change to the 15W40. High mileage vehicles will typically have greater clearences. I haven't had any trouble going to a thicker oil in summer in my older vehicles. The owners manual usually covers a vehicle during the warranty period, hence the specific oil reccomendation. However I would look into whether the oil consumption is internal only or external or a combination. If it is valve cover gaskets, rear main then this are straight forward to have replaced. (rear main being more time consuming). Depending on which part of the country you live in I would go back to the lighter oil in the winter for ease of starting. Here in South Dakota, it can get to 20-30 below real easy.
Hope this helps.

 

OK, that makes sense... the book covers the warranty period, and during that time the engine is new and thus needs a thiner oil... ok I get it now.

It's good to know that we should be ok. we've been running it and haven't seen any new problems show up. the oil consumption has decreased also, which may be due to a lack of freeway driving at 80mph on a daily basis now... he used to commute to work in it daily and it would loose a quart about every two to three weeks. it doesn't smoke so there may be a leak somewhere.

In south Carolina it never gets below zero. Last winter I went down to 10w40 just in case and it was fine... the coldest we got was like 18 degrees....

thanks,
-Mike-