The ETA "5" diesel was the first model engine to be produced by ETA Instruments Ltd. of Watford in Hertfordshire, England. It was a basically conventional 5 cc sideport diesel of its time and place. It made its initial market appearance in July 1947.

The ETA “5” was primarily designed by Eric Bedford, the older brother of ETA's more famous designer Ken Bedford. It was a good runner, albeit somewhat inflexible in terms of its operational speed range. It was noted for its fine workmanship and for the excellence of its castings at a time when many British "garden shed" products lacked such positive attributes.

The standard “CI” version of the ETA "5" had a tank and cut-out, but in mid 1948 the engine also became available in a somewhat simplified and lighter “R” version for control-line and tether car applications. This version was distinguished by a red-anodized cylinder head and spinner as well as a shorter intake venturi with no attached fuel tank.

The ETA "5" remained in production through several variants until mid 1950. It was still being advertised as of May 1950 alongside the later ETA glow-plug models. However, that May 1950 placement marked its final advertising appearance.

A detailed article by the late Ron Chernich about the ETA "5" may still be accessed on Ron's now-frozen but still hugely informative "Model Engine News" (MEN) website.