Oil Change

I suppose this post could be re-titled as "beating a dead horse", but here's another on synthetic oil.

My understanding is that (perhaps not all brands or types of) synthetic oil, and indeed many (notice I'm hedging my bets by not saying all) of our other "super chemicals" start their life as a petrochemical - that is (for anyone out there who doesn't know) based on our good friend, OIL. Somebody please tell me if I'm incorrect. Granted, ICE friction is reduced by using this stuff, but are we laboring under a possible misconception that we are helping to divorce ourselves from the oil producing universe by buying synthetic motor oil? I'm going to start searching the available information and see if there is any quality synthetic oil that is not derived from petroleum. Perhaps if there is, the cost is prohibitive and the durability is inferior.

Bruce Webster[/u]

 

My 2 cents,
If the ultimate goal is to use up as few dinosaurs as possible, the best oil choice would be recycled oil. There is spotty availability though. I use to be able to find it in my area but no longer seem to be able to. Kings County in Washington as well as other places actively support its use. Recycled oil has to pass the same standards and is graded the same way as new oil and as far as I was able to find in researching the topic is no different from the same grade as "fresh" dino oil.

 

jchu,

That is an excellent point. And, for those who are somewhat squeamish, you should at least consider it for your less precious ICEs (e.g., power equipment, high mileage vehicles). Still, I would like to see a breakdown of the environmental impacts of using recycled oil.

 

More on recycled oil,

For all those interested in saving dinosaurs and "closing the loop" but are squeamish about using recycled oil and want to know more first, Google the term "Rerefined Oil" will get you the most precise result. Rerefined oil has to pass the same API standards. They repeatedly point out that the only problem with used oil is that it gets dirty. Many of the sites are government sponsored. Did not really see any in the first page of the search that was by a specific company trying to push their product.

Just adding a little more to my 2 cents.
jchu

 

Another thing to keep in mind about octane ratings, lower octane gasoline has more energy per gallon than high octane fuel. It seems contrary to logic, but you will get better milage with the lowest octane gasoline that your car will burn.

 

My dealer recommends changing oil every 3,000 miles instead of 5,000, so I am within a week or two of my second oil change. The maint-requ light came on at 4500 miles; they said they would set it to a 3,000 mile interval next time I am in. Can any of you suggest a purpose for the 3,000 mile interval other than the dealer's self-interest?

 

Evan, I thought as much. Thanks. EF

 

Toyota's specified 5,000 mile claim probably has validity given the unusual ICE design and operating parameters. However, the dealer's claim that 3,000 miles is best is slippery at best. I'd take any of their advice with a degree of doubt.

 

On reading these three pages of messages I'd like make a couple of comments:

1. My last car had a 1.8 litre turbo engine. Audi called for 10,000 mile intervals between oil changes (they had called for 5,000 mile changes on their previous version of this same engine). This prompted me to do research on both dyno and Synthetic oils. I did a lot. To make a long story short, after research I switched to synthetic and bought into the 10,000 mile oil change schedule (I'm talking about true synthetics like Mobil 1, Kendall GT-1, Valvoline Synpower, and the like). By the way, after I switched to synthetic oil, my carefully monitored gas mileage improved by 1 MPG (~4%).

With the Prius, I feel comfortable with 5,000 mile intervals in that our engine turns on and off so often. Based on my earlier research though, I'll still go with a good synthetic that I know will hold its qualities for that duration regardless of engine activity.

One other point on oil, I became concerned when I read that several of you found your engines over filled with oil (will cause oil to froth up resulting in, amoung other things, poorer lubricity). At least if I supply the oil (4 quarts of Mobil 1 from Walmart with 1/10 quart removed from one of them), I shouldn't have to worry about the overfilling problem.

2. One individual wondered why so many of the European and Japanese engine evaluations were done with higher octane fuel. They're not. Much of the world uses octane defined by RON (research octane number). The U.S. uses a different octane number system, the aki index, the average of RON and MON (motor octane number). Look on your pump and you'll see "(R+M)/2". RON turns out to be a number about 4 points higher than the aki number for the same fuel.

Here's some interesting reading on the subject:

http://www.btinternet.com/~madmole/Referen.../RONMONPON.html

And here's something that Union 76 wrote up.

Octane

The octane quality of a gasoline is its ability to resist detonation, a form of abnormal combustion. Detonation occurs when the air-fuel mixture reaches a temperature and/or pressure at which it can no longer keep from self igniting. Two types of abnormal combustion are common: the first is detonation as previously mentioned and the other is preignition.

Detonation occurs after the spark plug has ignited the air-fuel mixture and the flame front is moving smoothly across the combustion chamber. If, during this burning process, the unburned air-fuel mixture reaches a temperature and/or pressure at which it is no longer stable, it burns very rapidly causing a new flame front to collide with the one that originated at the spark plug. Maximum pressure in the cylinder occurs before the piston reaches top dead center (TDC) and that pressure try's to push the piston down before it is ready to go down. Piston burning and rod bearing damage are the result.

Preignition is the other bad actor and is usually started by a hot spot in the combustion chamber which causes the mixture to ignite before the plug fires. Under wide open throttle conditions, preignition will destroy pistons in seconds.

Research Octane Number (RON)

RON is determined in a single cylinder variable compression ratio engine that operates at 600 rpm with a 125 degree inlet air temperature at standard barometric pressure. Spark advance is fixed at 13 degrees btdc. In a real world engine, RON is necessary to satisfy part throttle knock problems.

A good quality racing gasoline has a RON in the range of 110 to 115. The difference in the spread of RON is not very important to racing engines.

The test and hardware were originally developed in 1931. The hardware was revised in 1946 with procedural changes made until the late 1960's.

Motor Octane Number (MON)

MON is determined in a single cylinder engine similar to the RON engine with a few changes that make operating conditions more severe and therefore the octane numbers are lower. The MON engine runs at 900 rpm with a 300 degree mixture temperature. Spark advance varies with compression ratio. In a real world engine, MON is necessary to satisfy octane demands at wide open throttle. This is a very important number for racing engines since they spend a high percentage of their lives under high speed and high load conditions. Racing engines cannot afford to be short on octane quality, since detonation or preignition will quickly reduce a racing engine to junk.

The motor octane appetite of an engine with 13:1 compression ratio and a four inch bore varies with operating conditions but is normally around 101. Good quality racing gasolines have MON in the range of 100 to 115. If your engine requires a 101 MON, it is of no value to use a gasoline that has a 115 MON. To cover yourself for extreme conditions, it is wise to have an octane cushion but there is no advantage to using a very high octane quality product if you do not need it.

The MON test was originally developed in 1932. Major hardware changes were made in 1948 with procedural changes made until the late 1960's.

(R+M)/2

This is the average of RON and MON. It is sometimes referred to as the aki or anti-knock index. By law this number must be posted on the dispensing pump at retail outlets in most states. It is the most commonly used octane reference today. It was developed about 20 years ago as a compromise between RON and MON for advertising purposes and also to keep from confusing the consumer with too many different terms. It has erroneously been referred to as road octane number.

 

I talked with my dealer about using synthetic oil and they said I needed to wait until I broke the engine in before using synthetic oil. They said about 12000 miles.


SB waiting on my Black 04 #9 since 11/93

 

My dealer was just the opposite.

I went in for my complementary 1K Oil Change and they asked "Do you want to switch to Mobil1 now or wait til your 5K oil change?"

Apparently they assume all Prius owners are going synthetic, hehe.

It's $20 more per change from them for Mobil1

They do stress that once you switch, you can never go back.

 

Could someone explain exactly why once you

switch to synthetic you can never go back.

Jon