Hello, from Seattle.
New to slantsix.org
Not so new to the slant six world
First car (gifted by my grandparents) was a 1978 plymouth volare station wagon, silver with red interior. Ive owned three since then.
Current is a 1976 plymouth valiant broughm 2 door hardtop.
Questions for everyone
1. The serial Number (behind alt bracket) is 6225 r10 6L
i think i know, just want it confirmed.(and what about the letters in the sequence?)
2. If original (just bought the car)does that fall into the year of a forged crankshaft or cast iron? And if you are NOT-racing your slant 6, what if any, are the virtues or downside to each of these cranks. Is one better than the other? Why did Chrysler make the change? Ive been researching this and cant seem to pin a timeline down on when chrysler started that change.
3. And last, If anyone replies, could you please tell me what viscosity of oil you use for your slant six. Especially if you use it as a daily driver or drive often. I just want to get a read on what the average might be.
Thanks very much in advance for any response.
Please keep this great community going.

Welcome here. Post a clear, sharp photo or an accurate transcript (line by line) of the fender tag under the hood on the driver side inner fender, stamped with letters and numbers, and we can tell you a great deal about where, when, and how your car was built.

Engine stampings can vary widely in their format. Yours probably decodes as follows:

6: Model year 1976
225: Engine displacement
R: Passenger car engine (vs. truck/van)
10 6: Engine built on October 6, 1975
L: ??? Unknown.

If that last figure is an "E" rather than an "L", then this is a cast-crank engine. If it is an "L" and the date code is correctly decoded, then it is a forged-crank engine. The changeover from forged to cast was after 1976-model production had already begun. The cast crank is lighter and was less expensive to manufacture. The bearings, however, are smaller. The benefits and drawbacks are theoretical until you get into extreme racing; for normal vehicle use there is no practical reason to prefer or shun one or the other.

There is no good to come from looking for an average oil viscosity The optimal viscosity depends on the condition of the engine and the ambient temperatures in which it is used. It is common and unwise to pick an oil of too thick a viscosity grade in the mistaken belief that heavier oils offer better protection; this is a holdover from long, long ago and in fact, heavier oils will worsen and accelerate the wear of an engine in basically good shape because heavy oil takes much longer to reach critical lube points on startup. An engine that is worn to the point of needing rebuild can be kept in service for awhile by leaning on the crutch of heavy-weight oils.

Me, on a slant-6 in good condition, I tend to use a 5w30 or a 5w40 in warm weather, a 0w30 or a 0w40 in (very) cold weather. I usually use synthetic, because it is really better in all the ways that count. I never go to the needless hassle and expense of buying specialty boutique synthetic oils such as Redline or Amsoil; I use recognised national brands that are available everywhere (Mobil-1, Pennzoil, Valvoline...). I change it every 6,000 miles or so in difficult conditions (cold weather, short trips); longer than that in easy conditions (warm weather, long trips), and these are overly-cautious intervals. Changing oil every 3,000 miles is a big waste. There is generally no reason or need to add anything to the oil.

It is important to use a good filter. Never a Fram, and always a tall filter. NAPA Gold #1806 or Wix #51806 has a built-in standpipe that helps speed oil delivery to the bearings on startup. Fleetguard #LF3487 is an ultra heavy duty synthetic-media filter that does a very good job over a very long lifespan. But NAPA Gold #1515, Wix #51515, Purolator #L30001, and Motorcraft FL-1A are all fine choices, too.

It will also be a good idea to service the oil pressure relief valve to make sure it's doing its job, as described in these two threads: thread 1, thread 2.

Please feel free to post pictures anywhere on the board. Keep the viewing size and the file size reasonable so as not to blow up the page view or slow down the load speeds.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

just out of curiousity, why not a fram, ive always used them and i think they workpretty well. Bad experience?

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87 Dodge B150 Slant 6 Auto

Hi, I am an auto technician, ASE certified, and also a long time user of Fram filters. I have seen these filters cut open and compared to Wix, Hastings, etc. and they really are crap. I use them because, unlike Dan, I prefer to change my oil and filter every 3000 miles so i use cheap oil and cheap filter. I just wouldn't sleep at night knowing I ha 5000 plus miles on the oil in my rigs . My DD F150 has 231k on it and still going and my wife's explorer has 168k. Both of these have had fram filters and cheap oil since new, but I change it every 3000 mi.

Just my $.02
Kevin

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crossthreads are better than locktite