Oil change frequency for fully synthetic and light use?

[lordoeuf]

I've been having a tough time finding a more definitive answer to my specific case for oil change frequency.

I have a 1999 Jeep Cherokee with 110K miles on it. I live on Vancouver Island, so the climate is very mild year round. I use 10W30 Valvoline fully synthetic motor oil. The Jeep sees about 3000 miles per year in street driving. The average trip length is about 3 miles. How often do I need to change the motor oil? Perhaps every 2 years, or are there emulsifiers in the oil which would have sufficiently broken down by then?

[asymptonic]

Work with a used oil analysis firm to extend your OCIs scientifically. Otherwise I think the rule of thumb for synthetic is double that of ordinary oil.

[Unclewolverine]

Originally Posted by asymptonic

Work with a used oil analysis firm to extend your OCIs scientifically. Otherwise I think the rule of thumb for synthetic is double that of ordinary oil.

Under usual conditions. I would be hesitant to leave oil in for years at a time.. But as far as type and viscosity, man, that's a can of worms! Everyone has their own opinion and some people can get heated about it. Personally I use 15w-40 rotella and change at 3k. Which is about once a month for me.

[RCP Phx]

I've been running Amsoil for 50yrs but I still use the regular service change schedules just because I care about my motors. If nothing else change the filter and add a quart if just need some time.

[75SV1]

I've been using synthetics since the late 80's. Not exclusively though. With out a lab results, I would not go beyond 8K on an OCI. I have exceeded that though to near 12K. It would also be depended on how clean the engine runs. Now, not exceeding that mileage, I've always tried to change synthetics in a years time. It used to be 3 months for dino. The dinos have gotten near synthetic performance in the past 5 years. So, I might extend them to 6 months.
I am running Rotella T6 in my XJ the 5W-40.
I think AMSOIL has a 25K or more OCI on their oils if you used their extended filter. I'm by no means an expert on this. Still, If I were you, 8K and 1 year is what I'd go with.

[techno1154]

Originally Posted by asymptonic

Work with a used oil analysis firm to extend your OCIs scientifically. Otherwise I think the rule of thumb for synthetic is double that of ordinary oil.

In addition to the above comment, I would add 3 miles per trip put you in a very negative position. The XJ need, at least my XJ need a lot more than that to come up to the proper temperature. The oil and engine for that matter is not hot enough to evaporate all the moisture in it. More frequent oil changes and/or oil analysis may be needed.
I live in Florida. I use Amsoil. The manual allows up to 7,500 miles depending on conditions between oil changes. I change the oil between 12 and 15,000 miles. With 350,000+ miles on my XJ. It have 60 PSI pressure cold and 40+ at idle after a long run.

[lordoeuf]

Originally Posted by 75SV1

If I were you, 8K and 1 year is what I'd go with.

Do you mean "8K or 1-yr, which ever occurs first"? If so, I'm at the 1-yr mark. To date, I have 2125 miles on my latest oil change, which occurred exactly one year ago today.

The Jeep sees a 3-mile, 12-minute drive to my kids primary school at 8:30 AM, then a 3-mile, 12-minute drive back home. Then in the afternoon, another 3-mile, 12-minute drive to pickup the kids, and a 3-mile, 12-minute drive home. Temperatures where I live are nominally around 6 - 10 C in the winter, and 14 - 24 degrees C in the summer. Is there not some online calculator or other rules of thumb to narrow in more on more optimised oil change frequency based on user input? At 2125 miles in 1 year, it seems a bit wasteful to be changing the oil again.

I contacted an oil analysis company in Edmonton Alberta, which is the closest I could find to me in BC. The pre-paid cost for the analysis is $62 CAD, which is about the cost for me to change the oil. If I didn't need shipping, it would be $39, but I was unable to find a local outfit in my town.

In the past, I had been changing it every year based on about the same driving frequency, but was starting to think that maybe it could be pushed to every 2 years.

[75SV1]

I was told or read to change synthetics once a year. That has been several years ago, say 20. As mentioned before oil is hydroscopic, ie collects water. Synthetics are less hydroscopic that conventional oils. It takes about 30 minutes at temp to 'burn' off the water. This also applies to brakes and other stuff. I would plan to run at least 30 minutes once a week or at least monthly.
The oil analysis should be viewed as to how your engine is doing. If you want or plan to exceed the 1 year or 8K mileage. So, it might be savings in the long run. No, I haven't had one done yet. Also, it might warn you of potential problems.
Also, the 7,500 or 8,000 OCI in manual are for non-severe driving. That is mainly highway driving in non dusty conditions. City driving is or could be considered severe.

[Black1990jeep]

Your short drives are considered hard use, thus you should change the oil frequently. contamination build up is the major issue when you only drive it 3 miles at a time. The engine is running rich when cold, water is introduced as a by product of combustion, yet the engine remains cold, so the water and fuel in the oil does not get heated away.

Id switch to cheaper oil so as to afford the more frequent oil changes your type of driving requires. No matter how good and pricey sythetic oil is, if it is contaminated from hard use, like many short trips can do, well you NEED an oil change. As a rule of thumb, one year in the crank case regardless of total miles, if oil shows signs of foaming, or other contamination, then more frequemtly.

The thing to keep in mind is your usage is considered hard use, frequent short trips, without full warm up.

So once a year minimum, no matter the oil type, that is how often I would change it if my rig.

[lordoeuf]

Black1990jeep, thanks for the additional insight. Would it not be more appropriate to consider that 3 mile trip to school as a 6 mile trip? The vehicle is only shut off for two minutes to walk the kids to the door, then it is turned right back on to drive home. Hence, is a 6-mile, 24 minute run time twice a day still insufficient to increase oil change intervals? The engine is up to temperature (210 F) after about 6 minutes of driving.

[asymptonic]

Sure, you can probably figure it that way, but either way the majority of your uses are short trips, so I'd either change the oil more frequently with cheaper oil, or spend the small amount of money to determine what's really happening in the engine to see if the synthetic is benefiting.


Point is you're spending money either way. The only way to know if you're saving money or oil changes is to have it looked at. If you don't want to do that use ordinary oil and change it as recommended by the owners manual.

[Johnnie Walker]

In theory, full synthetic oil takes a very long time to break down. That said, I would at the very least, once a year change the filter and top off the oil. And do a full change every other year.

Definitely have your oil analysed. Send in the new oil sample, and used oil sample to get a base line.

[JonnyCat63]

I usually change the oil in my fleet of junk every 3000-4000 miles. My trail rigs are changed once a year at the minimum. Sometimes the rigs don't see but a few hundred miles in a year, but once a year at the very least seems reasonable to me. Since I'm obsessed with vehicles, and we have 4 drivers in our household, I change a lot of oil.

Is there an issue with changing the oil once a year for you? It seems like a minor inconvenience and a minimal cost to do for peace of mind.

[75SV1]

Another aspect is the filter. For the OP's mileage a standard filter would work. If you're going over 5K OCI, then the extended OCI filters should be used, or as suggested previously, to change the filter and replace oil lost. I use NAPA Platinum filters.

[lordoeuf]

Thanks everyone for their responses. I have decided that I will be ordering the oil analysis. The guy said that they have a database of existing oils, so they don't need a baseline virgin sent in.

I'm interested in the suggestions to use the cheapest filters and cheaper non-synthetic oil and just change it once per year. I went for fully synthetic and the mid-range filters thinking I could extend my service intervals, hopefully out to 2 years. Thus, if I went with petrolium based or a hybrid oil, could I change the oil just once per year with the given driving conditions? My 1979 diesel Benz only sees about 2,000 miles every 2 years and I've been sneaking by with an oil change every 1-2 years using Shell Retega 15W-40. The car burns oil though, so it tends to get topped up about a litre per year. Might get that oil analysed as well...

When I recall my time living in the US, I noticed that those quick lube places for $15 oil changes are on every corner. In Canada, there aren't nearly as many of them and the last time I went in there to change the Jeep's oil [in Canada] the cost was around $70 (and I had a coupon!). So I've been doing all my own oil changes. The next problem came a few years ago when Canadian Tire and other local garages stopped accepting used motor oil. Now I need to drive the oil all the way to the landfill for recycling. I also do not enjoy changing the oil - no matter how much I prepare, it always makes a big mess. In addition, the costs of the filters have gone up quite a bit in the last few years, as has the price of oil (surprising given the drop in crude price). For all these reasons, I'm trying to extend the oil change intervals.