One of the more common questions I get is about which is better; natural or synthetic and when to change it. I can see the deluge of mail coming in already...
Question: Oil And Oil Changes
Greetings Vincent, My name is Donald and I have a 2003 Nissan Maxima SE and I have been using synthetic motor oil for about 2 years now. The car has been running well but I have a question, do I have to change every 3,000 miles or can I change every 6,000? Also I was told that once you use synthetic you can not go back to standard oil because it will cause a problem with your engine.
Thank you,
Donald
Answer:
There is a great ongoing debate about oil types and when to change it. I always said to keep a friend never discuss politics, religion or oil changes.
Synthetic and natural oils, with rare exceptions, are completely compatible. So mixing them is not an issue. There are some who say that seals and gaskets get "used" to synthetic oil but I have never seen documented proof of this one way or the other.
So that leaves oil change intervals. I just did a random sampling of several of my service manuals and each one recommends almost the same thing. But since you have a 2003 Nissan Maxima let's see what Nissan says. Under normal service change the oil and filter every 7,500 miles. Under severe service replace the oil and filter every 3,750 miles.
So now we need to define normal and severe service. From the Nissan service manual:
SEVERE SERVICE
Follow the Severe Service Schedule if your driving habits frequently include one or more of the following driving conditions:
- Repeated short trips of less than 5 miles (8 km).
- Repeated short trips of less than 10 miles (16 km) with outside temperatures remaining below freezing.
- Operating in hot weather in stop-and-go "rush hour" traffic.
- Extensive idling and/or low speed driving for long distances, such as police, taxi or door-to-door delivery use.
- Driving in dusty conditions.
- Driving on rough, muddy, or salt spread roads.
- Towing a trailer, using a camper or a car-top carrier.
NORMAL SERVICE
Follow the Normal Service Schedule if none of the driving conditions shown in Severe Service apply to your driving habits.
Okay, so now we know there aren't too many people who drive under normal conditions.
Now, why do we change the oil? Because it breaks down. Well to a certain degree yes. But it may take as long as 20 years for a motor oil to break down. (Clear out the mailbox 'cause there's a flood on the way.) The main reason we change oil is because it gets dirty. Natural and synthetic oils get dirty at about the same rate so it seems logical that if a natural oil gets dirty enough to change in 7,500 miles wouldn't synthetic oil be just as dirty and need changing in the same amount of time? What good is an oil that will last 50,000 miles if it gets dirty enough to have to change at 10,000 miles?
Would you want to leave dirty oil in your engine for 50,000 miles? And it's not about making money either, no mechanic ever got rich doing oil changes.
So let me boil it down to this; if you use a decent quality 10W-30 engine oil with a decent quality oil filter and change it every 3,000 miles or so your engine will last a good long time.
