At 04:21 PM 8/19/2010, mcneely4@cox.net wrote: >David, I may be wrong (never happened before ;-) ), but I think >there are some incompatibilities in materials, such that chemical >interaction, or lube problems may occur whenever 4 is substituted >where 3 is specified or vice versa. There are some differences in >chemistry, hence the different names. If DOT 4 fluid could always >replace DOT 3, why wouldn't the manufacturers just drop the DOT 3? No doubt because it's less expensive. But -- as of 2003 ChevronTexaco thinks resellers ought to only carry DOT 4: "Widespread suitability for different motor vehicles provides inventory benefits since all conventional systems can accommodate DOT 4 fluids, and vehicle manufacturers are increasingly specifying this level of performance." They cite these applications: All hydraulically operated motor vehicle braking systems (drum and disc types) for which a DOT 4 or SAE J1704 fluid is specified Make-up *or service fill* [my emphasis] of braking systems requiring DOT 3 or SAE J1703 fluids Vehicles with anti-lock (ABS) braking systems Hydraulic clutch systems requiring conventional fluids Passenger cars, commercial road transport, offhighway vehicles, agricultural tractors and motorcycles For vehicles operating in extreme service conditions, or where a DOT 5.1 fluid is specified, Caltex Brake and Clutch Fluid DOT 5.1 is recommended. Not to be used in systems designed for mineral oil based fluids (LHM), e.g., certain Citroen models, or where Silicone DOT 5 fluids are recommended. http://japcokwt.com/pdf/Brake%20Fluid%20Dot%204.pdf >but I'll check later to see what if anything the book states, beyond >specifying a fluid. I'd be extraordinarily surprised if it didn't say use DOT 3 or DOT 4 but never never never use DOT 5. There is now a DOT 5.1 (terrible nomenclature) that is once again backwards-compatible with other glycol-based fluids such as 3 and 4. Look on page 140 or in the near vicinity. Yours, David |
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