What engine oil to use?

You are going to be very happy next January, Greg!

Toyota recommends their 5W30 conventional oil. IMHO, conventional oil is fully adequate for 5k mile oil change intervals (OCI). But if you buy your oil at the corner store, note that there are a bunch of capital letters that need to appear on the oil bottles you buy. See those in your soon to be seen owner's manual.

I use Mobil 1 synthetic, and do extended OCI. Used oil analyses are our best tool to know how far it is safe to go in that area. Have noted no obvious changes in performance, fuel economy, or anything else. But I am buying and recycling less engine oil. Approaching 80k miles, it seems unlikely that an engine warranty dispute could ever arise with Toyota. We now have evidence that Prius is very easy on its engine oil. I *know* that Tochatihu is squeaky-clean inside.

I suppose everybody wants high mpg in their Prius, but switching to synthetic oil is not the magic bullet. Learn the driving tips posted around here, combine short trips whenever possible, don't drive on underinflated tires or overfilled engine oil, keep the engine air filter clean, don't let your parking brakes drag, and stick to the posted speed limits (or a bit slower, if you can stand it). I do my best in these areas, and still only average 46 mpg in 2001 Prius. You will probably to better.

 

Congrads on the new Pri. All Lex/Toy/Scions start life with normal 5w30 oil from Mobil 1, relabled as toyota oil.
The use of higher grade oils (synthetic or blend) will not void any warranty.
Synthetic oil was developed in the 70's to keep constuction equipment running in the bitter alaska cold durring the oil pipeline days. Normal oil would near instantly gel in the cold.
The benifits do not always out weigh the costs. I'll use our shop as an example.
LOF: 26.95 interval 3000 miles
LOF blend: 34.95, interval 4000 miles
LOF synthetic: 54.95 5000 mile interval
Oil is not as important as the change interval, I have no proof, just 25 years experiance on cars.
At our shop, blend gives the most bang for the buck, but I do feel full synthetic sticks to components longer than normy or blend.
The most important thing I can tell new car owners is to overchange the oil....use good stuff and change it early. I run Mobil 1 full synthetic in my 03 IS300 and my sweeties 99 celica. Miles are 21000 and 52000. Never a drop leaked, inside of the 99's valve cover looked new, not just clean, new at 30000 durring the valve lash checkup. I do both rigs at 3500 mile intervals. Not 5k, not 7k, not 15k (yes I see that all the time).
The big thing about the Prius specificaly is only use 5w30 and do not overfill it. Since the Pri starts and shuts down often, it gets dirty faster because the oil rarely hits 200 degrees like other cars. The heat helps cook off moisture and acids.
More than once I have had Pri's with 4 qts from Jiffy lube and a P3191 engine code. Nomal cars do not monitor amperare varriations to the starter, but the Pri does. It looks at MG1 and MG2 torque and rotation. If it turns to slow because the oil is 15-40 or 1/2 qt or more over it sets a MIL.
I hope this helps some,
Regards, Mike

 

Thanks for your advice, Mike, and welcome to priusChat.

Are you a Prius tech? It's interesting to hear you say the Prius oil gets dirty faster. What distance on the highway do you think a Prius needs to drive to get to 200° oil temperature?

 

Lots of variables here Bill, but most cars require a 2000+ rpm modest load, for 20 minutes or so to realy heat the oil. This helps to vaporise normal moisture from condensation and purge it out the PCV. Unfortunately the Pri likes to go easy on the ICE. In town it is hard to get oil above 150 degrees. The oil gets dirty fast on intown drivers. We service more than probably any other dealer in the U.S. because the State, county and city all own pri's. Intercity transit, fire department, DOC, DOT, and AG office all use them as well as Evergreen coll. The oil is always water thin, and nasty black with a heavy acidic smell.
I recomend to all my customers who listen to do oil changes early and often, if you are going to skip maint. , skip brake checks , coolant flushes and tune-ups etc.
Regards, Mike

 

In city driving, especially here in Winnipeg, all cars are rough on oil. At -40 you can drive all day in stop and inch traffic and the oil will be lukewarm at best.

I first started using synthetics 25 years ago for the superior cold temp protection and longer engine life. I never expected fuel savings and have never seen them either.

I still have a 1984 Ford F-150 I bought new, now it's out at my hobby farm. Around 530,000km on that 302 V8 and the compression is still 130 lowest. Most of it's life it ran Mobil Delvac 1 5W-40, changed every year or two, with filter changes every 3-4 months.

At 18,000km I switched my 2004 Prius from the dealer 5W-30 (Rebranded Mobil 5W-30?) to Mobil 1 0W-30. No difference in fuel consumption but I much prefer the 0W-30 for our winters.

It should be at 24,000km before the end of the month. I'll do a used oil analysis as there is a lab here in Winnipeg that can test used oil. I'm curious about the moisture and TBN, as the vast majority of my driving is city.

 

This is music to my ears, Jayman. Please post the UOA results! The first time I took an oil sample for analysis, I took it "cold" (not following the instructions), and there was a "trace" of water present. Surely you will not repeat this rookie error.

Ifixem and Bill Merchant, my 2001 Prius with miniscanner says that 85C/185F coolant loop temp is typically reached within the first 5 minutes of driving, or 10 minutes if it's sorta cold out. Lacking an oil temp sensor, I can only speculate that the engine oil rarely gets to 200F. I realize that this can be important for chasing water out of the engine oil, but (when well-sampled) the Prius engine oil is not wet. If you have any ideas how to check this better, please post them.

Are you cold-world drivers blocking the radiator airflow during the winter? Even I do that, and most of California does not get cold. None of it gets *really* cold, at least not where the roads go.

 

ECT does not equal oil temp. I should also quantify thet I live in the NW corner of the US so arizona and cali drivers can ignore the water in oil issue. Around here it is above 50% humidity for 9 motnh a year. Wet air in means more condensation develops after you park it. About the only way to check it is with a themocouple down the dip stick hole. Then again, the ICE will not see the load other rigs do.
Regards, Mike

 

I agree with all of your points, Mike. Please say what you have found by measuring Prius engine oil temp vs the coolant.

It is a shame that Prius comes with no facility to monitor oil temperature nor pressure! But all we know so far from UOA suggests that they have not really short-sheeted us. The ICE is fully loaded sometimes, but not very often, I reckon.

I have driven up your way a couple of times, to chat with folks at Evergreen. The faculty parking lot was full of SUVs. We have a lot of work to do yet.

 

Mike now you know how i feel. i park at the Dept of Health over in Airindustrial park. thought my company was getting more progressive when i saw a dozen other Priuses there one day.

unfortunately, every single one of them was a state vehicle. finally have a co-worker who got an 05. also have a guy who just started working there who has an Insight... still has dealer plates on it though. still dont know who it is yet.

 

If my old Ford is any example, I can also state that coolant temp and oil temp rarely agree with each other.

When I bought the 1984 Ford F-150 new, I put on a Stewart Warner mechanical temperature gauge (Using a spare threaded outlet on the cast iron intake manifold), and a Stewart Warner mechanical temperature gauge on the oil pan.

I took off the oil pan, drilled the proper hole near the bottom third of the oil pan, put the capillary sensor on, then put the oil pan back on. Took a day to do that too. Around 10 years ago I had to replace the Stewart Warner gauges and put on Autometer Pro Comp mechanical gauges.

I usually ran a 180 thermostat in the truck, except when I had it in Utah and Nevada and ran a 160 thermostat.

Up here with a 180 thermostat, and not using the winter front, at -18 C or 0 F and colder, the engine struggled to reach 180. In town driving the needle would barely go above 140 F. The oil temperature gauge would never leave the bottom peg of 120 F.

With the winter front on, the motor would usually reach 180 after 3-5 mins of highway driving, or around 10-15 minutes of town driving. The oil temp gauge would usually hover around 140 F.

The 1,000 watt circulation block heater I put on made a huge difference. The motor would already be at close to 120 F when I started it, and after 2-3 mins of driving it would be at 180. That's with the winter front on too. Oil temp around 140-160 F.

In summer the motor would usually reach 180 in 2-5 mins, and the oil temp would usually reach 180-200 in 10-15 mins. Down in Utah and Nevada even with a 160 thermostat, the oil temp was usually 170-200 F.

Oh, at the same time I put on the Autometer gauges, the guy I bought them from had a store return that was a bit scratched. I also put that one on too, using a spare threaded connection on the BACK of the Edelbrock aluminum intake, right near the firewall.

Consistently, the REAR of the block is a good 10-50 F colder than the front of the block, depending on ambient temperature. That makes sense, the coolant passages are such that return coolant from the rad is sent to the rear of the block , then it migrates to the front of the block.

I have never seen the rear of the block over 160 F, even running up that steep grade on I-15 between Mesquite, NV, and St. George UT. I have a custom made 5 row rad, maybe that helps.

Just because the oil sump or the thermostat housing is at a certain temp doesn't mean the ENTIRE block is at that temp. You could have air pockets in the block that could be causing localized overheating. That's why you should use one of those vacuum pumps to break all the air pockets in the block:

http://www.mityvac.com/pages/products_cse.asp

Oil that might be at 180 F in the sump might see temps of +800 F near the piston crown or piston skirt. Especially in cold weather 0 F and colder, expect a lot of condensation when you do shut it off.

 

The local lab is part of a large Caterpillar engine shop. THeir instructions state to ONLY sample motor oil at operating temperature.

They also would appreciate a baseline analysis to better gauge the oil degredation, so I'll give them a quart of Mobil 1 0W-30 to test as well. I'm curious what the TBN of fresh Mobil 1 is.

They can even run MRV testing to check cold temp pumping down to -40, but this test costs a small fortune. Apparently most of the trucking fleets run this test once in awhile to verify their oil is capable of safe operation at -40.

 

My recommendations

1) Amsoil ($6/qt)
2) Redline ($10/qt)
3) Mobil 1 ($5/qt)

Grade:

Always 5w30

Filters:
1) K&N
2) Mobil 1
3) Bosch

Mobil 1 is excellent, but there are better synthetic oils that are not found everywhere. I buy my Amsoil at a store called SUPER AUTO BACS in Orange County, CA.

Synthetic oils are worth every penny!!!

Benefits
1) Longer life (you can run it for 20,000 miles if you wanted, but 10,000 miles is a good interval)
2) Reduces engine wear and friction (Ever see those Mobil1 internal engine tests? Very little wear at 100,000 miles)
3) Flows easier when cold (critical while the engine is not fully warmed up)

Disadvantages
1) Sure, it's double the money (or slightly more), but it can also run at double the intervals!
2) Your oil shop or your garage will see you less often!

I always recommend full synthetic to all my friends. Do not go for regular or simply semi-synthetic blend. Lastly, you should switch at 5,000 miles or more because the engine needs to be properly broken in to have good compression.

To each his own though...

 

12.0 per liter for Mobil 1 5W30 synthetic, says Blackstone Lab. This is grams KOH equiv. or milligrams, I'm afraid I've forgotten which. I see that number as midrange among the fancy oils. There seems to be a lot of variation among the various TBN titration methods; we can comfortably ignore everything after the decimal point.

The exponential decay of TBN seems to have been well-established by those neptune spacebears guys, but perhaps the functional endpoint was not. Do I toss my engine oil at TBN 2, or 1, or some other number? Anyway, it seems clear that this will be the first thing to go; certainly not the measured viscosity of the Mobil 1 synthetics.

For now I am sticking with oil change at about 13k miles in Prius, with a filter change halfway. If anybody has data suppoting longer for either, let's see it.

DAS