just googled this, follow the link and look at the search results ...
skyline oil pressure sender bspt - Google Search
i think its a nissan/jap thing to use bspt for oil fittings - and a US thing to us NPT
some cut and paste text on the difference;
BSPT (British Standard Pipe Tapered) fittings found on most Japanese made parts and cars, is very similar to NPT (National Pipe Tapered) fittings commonly found in the USA, the only difference is in the thread pitch. NPT threads are slightly thicker than BSPT threads. BSPT male fittings can be installed on NPT female fittings using a liberal amount of teflon tape (not recommended for high pressure applications). However, do not try to install NPT male fittings on female BSPT ports, particularly on cast/aluminum parts, as it is possible to crack the part.