smh@mhuxl.UUCP (henning) (02/04/86)
> Do you really change oil every 7500 miles? You must place a low value > on your car. By the time 7500 miles has passed the oil in the crankcase > is about 1/2 gas and will not provide worthy lubrication. That is why > diesels need oil changes more often; the high compression forces fuel > past the rings and dillutes the oil. The same thing happens to a gas > engine, it just takes a little longer. The need for oil change is not > because the oil is dirty, just dilluted. I have noticed that after 5,000 to 6,000 miles on an oil change, that I am not getting good lubrication to my valves/overhead-cam. The valve noise starts getting louder. I don't see how a manual can recommend 7500 miles when the oil doesn't last that long. I am talking about Sears Spectrum 10w-30 in a Volvo 245. As soon as I change oil/filter, the valve noise goes away.
piner@pur-phy.UUCP (Richard Piner) (02/06/86)
Change your oil often. I know the car makers try to tell people new cars only need an oil change every 7 or even 10 thousand miles. This is horse hockey. Break down of the oil is not the limiting factor. Dirt is. Modern oils have detergents to suspend dirt in the oil. So your oil isn't just lubricating your engine, it is washing it. Like wash water, the oil can only suspend just so much dirt. You want to replace your oil before it is saturated. Also, for this same reason, you want to change your filter at every oil change, since it holds a quart of dirty oil. I only drive about 7 thousand miles a year, but I change oil and filter every four months without fail. I've managed to keep a Vega running for 12 years following this practice, so I must be doing something right. Richard Piner piner@pur-phy.UUCP
mrl@drutx.UUCP (LongoMR) (02/06/86)
A long time ago I made a couple of observations . They were: 1) With a tight engine (i.e. no leaks) my oil level would remain full right up to about 3000 miles after a change. Between 3000 and 3500 miles the oil level would drop a quart. This told me that at about 3000 miles something was happening to my oil and probably should be replaced. 2) Oil filters are about $2.50 when you catch them on sale. To save $5.00/year it didn't seem reasonable to change the oil and leave the dirt every other oil change. 3) Cost of an oil change is about $7.50 w/5 quarts of oil and a new filter (on sale, which oil and filters always are!) It didn't (and still doesn't) seem reasonable to mess around with synthetics when petroleum based lubricants are proven to protect an engine and a change of oil and filter takes about 20 minutes 4 times a year (I drive about the average of 12,000 miles/year) --Just bein' practical-- -- Mark R. Longo ihnp4!drutx!mrl (303) 538-4900
halb@tekig5.UUCP (Hal Bates) (02/07/86)
In article <529@mhuxl.UUCP> smh@mhuxl.UUCP (henning) writes: >> Do you really change oil every 7500 miles? You must place a low value >> on your car. By the time 7500 miles has passed the oil in the crankcase >> is about 1/2 gas and will not provide worthy lubrication. That is why >> diesels need oil changes more often; the high compression forces fuel >> past the rings and dillutes the oil. The same thing happens to a gas >> engine, it just takes a little longer. The need for oil change is not >> because the oil is dirty, just dilluted. > >I have noticed that after 5,000 to 6,000 miles on an oil change, that I >am not getting good lubrication to my valves/overhead-cam. The valve noise >starts getting louder. I don't see how a manual can recommend 7500 miles >when the oil doesn't last that long. I am talking about Sears Spectrum >10w-30 in a Volvo 245. As soon as I change oil/filter, the valve noise >goes away. The overhead-cam shaft gets its lube from the engine oil pressure supplying oil that is forced up through the head, out through samll passages, and hit the cam assembly (sometimes). Some motors are set-up with a cam sprayer. A cam sprayer is a good modification to make to any overhead-cam motor. Anyhow, as the engine gets hot, the old thinned oil will result in a lower oil pressure (more severe at idle). If your Volvo has a "good" pressure guage, notice if this is occurs. If the valves are slightly out of adjustment the noise will be more noticable. Oil is the life blood to an internal combustion engine. Dont use a cheap brand to save some money. And change the filter. I hear that some people actually use the same filter after the oil change. I suppose the advertised 25000 mile rating on some filters must work. The consumer says "I have only 7500 miles on this filter. Must mean I can reuse this sucker." I really dont understand how or why the manufactures make that claim. It is totally misleading. I run Valvoline 20W/50 in my comp prepared motor and I run the same oil in my street rig also. Note - not the Racing oil. Racing oil lacks the detergent, it is good for high RPM applications (anti foaming and low detergent) but poor for long-term motors. Disclaimer I do not work for Valvoline. Just been around racing for a few years and know what is used and what I prefer. Hal Bates tektronix!tekig5!halb