vibrations under heavy braking. Engines The E28 was the first 5 Series produced with diesel engines (the 524d and 524td models) and with a petrol engined model specifically aimed at increased fuel economy (525e/528e model). The four models available at the launch of the E28 were the 518, 520i, 525i and 528i, with the 518 using a straight-four petrol engine and the other three models using a straight-six petrol engine. Over the course of the E28 model, the following models were added: the 524d and 524td using diesel engines, the 518i (a fuel-injected version of the 518), the 525e/528e as fuel-economy models, and the upper-specification 533i, 535i, M535i, and M5 models. A liquid petroleum gas (LPG) option was introduced for some petrol engines in 1984. Petrol 518: Sold only in some European markets where it suited local tax categories, the 518 was the lowest specification model which used a four-cylinder engine with a carburetor. Factory performance figures for the manual transmission cars are a top speed of and 0–100 km/h acceleration in 14.0 seconds. 518i: The base model in Japan and some European countries, the 518i used a fuel-injected four-cylinder engine. Factory performance figures for the manual transmission cars are a top speed of and 0–100 km/h acceleration in 12.6 seconds. This version was not sold in Germany until the 1984 facelift, when it replaced the carburetted 518. 520i: A mid-range model with the smallest of the available six-cylinder engines. Factory performance figures for the manual transmission cars are a top speed of and 0–100 km/h acceleration in 11.4 seconds. 525e / 528e: The 525e (called 528e in North America and Japan) uses a 2.7-litre 6-cylinder M20 petrol engine which is optimised for fuel economy and torque at low engine speed, rather than the traditional high revving characteristics of BMW straight-six engines. The "e" stands for the Greek letter eta, for economy. According to BMW, the 525e is more fuel efficient than the 520i, which has the same rated power of 92 kW. Since many markets tax cars based on engine displacement, the eta's larger engine meant that it was not suitable everywhere. The model was expressly developed with the American market in mind. BMW's corporate average fuel economy was at risk of not meeting requirements by 1984, primarily due to higher sales of their bigger, more expensive cars in the early 1980s. In Austria, the 525e was detuned to