1970
Only detail changes were made including a new split grille that no longer extended to surround the headlights and slightly revised rear section. Powertrain selections were carried over from 1969 with both 350 and 455 cubic-inch Rocket V8s now featuring "Positive Valve Rotators" for longer engine life and more efficient operation.
1971-76
All GM B-body full-size cars were enlarged for 1971 and now rode on a 124-inch (3,150 mm) wheelbase. It was available as a pillared four-door Town Sedan, two- and four-door Holiday hardtops and a convertible. Series models for 1971 included the base Delta 88, Delta 88 Custom and Delta 88 Royale, the latter inheriting the convertible body style previously offered on the base Delta 88.
Also new for 1971 was the Custom Cruiser station wagon, the first full-sized Olds wagon since 1964. It used the B-body of the Delta 88 on a longer (127 inch) wheelbase chassis that matched the larger and more luxurious C-body Ninety-Eight, but on its own loner chassis similar to other GM full-sized wagons with multi-leaf spring suspensions that differed entirely from the all-coil suspensions used in sedans and coupes. The Custom Cruiser came standard with the larger 455 Rocket V8 and utilized the disappearing clamshell tailgate of other big GM wagons.
Engine offerings again included 350 and 455 cubic-inch Rocket V8s ranging from 250 to 340 gross horsepower, all of which featured lowered compression ratios beginning in 1971 to enable use of lower octane regular leaded, low-lead or unleaded gasoline. Power front disc brakes were now standard equipment on all 88 models and beginning midway through the 1971 model year, Variable-Ratio power steering and Turbo Hydra-matic transmission were added to the standard equipment list.
For 1972, the Delta Custom series was dropped and the Royale series was expanded to include four-door Town and Holiday sedans. Advertised horsepower figures dropped to 175 for the base 350 two-barrel and 250 for the optional 455 four-barrel Rocket V8s thanks to an industry-wide switch in horsepower measurements from the previous gross method (as measured by a dynometer with no accessories attached) to the net method in which the power measurements were based upon an engine "as installed" in a vehicle with all emission controls and accessories hooked up.
For 1973, wider and lower spilt waterfall grilles flanked a new federally-mandated 5 mph (8.0 km/h) front bumper and larger one-piece rounded rectangular tailights replaced the four-segmented lights of 1972. Engine offerings included a standard 350 Rocket V8 with two-barrel carburetor (150 net horsepower) or optional 455 Rocket V8 with four-barrel carburetion and 215 horsepower (160 kW) with single exhaust or 250 horsepower (186 kW) with dual exhausts.
In 1974, a 5 mph (8.0 km/h) rear bumper was added and tailights reverted back to a four segment design similar to 1972 and the front grilles were narrowed and raised to hood level similar to 1971-72 models. Also, new rooflines were featured on Holiday hardtop coupes with fixed triangular side windows replacing roll-down windows of previous years. As Oldsmobile completely discontinued two-barrel carbureted engines this year, a new 350 four-barrel Rocket V8 (175 horsepower) became standard equipment with the 455 available as an option. Other highlights this year included an all-new flat instrument panel shared with Ninety-Eight and Toronado models with horizontal sweep speedometer and "Message Center" system of warning lights replacing the wrap-around dash of previous years. A new and seldom-ordered option available on all full-sized Olds models and Toronados was a driver's side airbag – among the first to be offered in a production automobile.
Detail changes for 1975 included revised grilles and tailights along with new rear quarter windows for pillared and Holiday sedans – the latter's design similar to an opera window. The same assortment of 350 and 455 cubic-inch Rocket V8s were still offered, but now hooked up to a catalytic converter that not only mandated the use of unleaded gasoline but also spelled the end of dual exhaust systems. 1975 was the final year for the Delta 88 Royale convertible, the last of which was built on June 11. Just under 7200 Delta 88 Royale convertibles were built in 1975 as Oldsmobile made a concerted effort to target the convertible buyer market at the time. The headline on a print ad for a 1975 Olds Delta 88 Royale convertible stated, "Today a beautiful Olds convertible. Tomorrow, a collector's item". The featured car in the ad was a pretty sharp looking Delta 88 Royale rag top, with the top down and looking good in red !
For 1976, the final year of this generation, the car received rectangular headlamps, with the parking lamps directly below instead of in the bumper. It was also the final year for the Holiday hardtop coupes and sedans, along with the 455 Rocket V8 and the optional airbag system that would generally become universal on production cars and trucks some 15 years later.
1977-85
There were now two body styles of the 88 on the GM B platform – the town sedan and the coupe – both pillared bodystyles. The 1977-1979 Custom Cruiser wagon was a Chevrolet Caprice clone.
The Royale name was removed from the trunk to become a simple interior trim option, the Royale Brougham in 1979. The next year, this became the high-line model of the 88, a position it occupied through 1983.
During these years, fuel economy mandates resulted in the use of smaller engines than before. Beginning in 1977, the standard engine was now a Buick 231 cubic-inch V6 with optional engines including Oldsmobile-built 260, 350 and 403 cubic-inch Rocket V8s through 1979. A few '77 Delta 88s, however, slipped off the assembly lines with "Chevrolet"-built 350 cubic-inch V8s, leading many angry customers to file lawsuits against General Motors alleging "fraud" because they had bought (and paid a higher price – compared to a similar Chevrolet) for Oldsmobiles on the premise they would be powered by Rocket V8s.
This situation was well publicized as the "Chevymobile Affair" and GM ultimately settled with affected Oldsmobile owners by offering "extended" warranties for the "Chevy-powered" Oldsmobiles, or the option of returning those cars in exchange for a "real" Olds with a Rocket V8 – however, the latter option was not often exercised due to the fact the owner had to pay GM back money based on the number of miles his or her "Chevymobile" was driven, which could become a very expensive proposition.
By 1980, the "Rocket" terminology was removed from Olds V8s although the basic engine design would continue through 1990 and advertisements for Oldsmobiles (and other GM divisions' cars and trucks) would include the disclaimer that "Oldsmobiles (or other divisions') are equipped with engines manufactured by various GM divisions, subsidiaries and worldwide affiliates."
From 1978 through 1981, a Holiday 88 coupe was offered, featuring Strato bucket seats along with console and floor shifter, along with Super Stock wheels and two-tone paint schemes.
The 1981 model was the first to include the Computer Command Carburetor in all 50 states. This system was the forerunner, and surprisingly similar to today's OBDII which is standard on all cars sold in the United States. The system read various parameters such as vehicle speed, throttle position, engine speed, engine temperature, and the oxygen content of the exhaust to provide the correct air/fuel mixture for any given driving condition.
Additionally, 1981 marked the discontinuation of the Oldsmobile "Rocket" 350 gasoline engine. The only V8 gasoline engine available for 1981 and later years was the Olds 307. The 350 remained available in diesel form, however. Also new for 1981 was the Turbo-Hydramatic 200-4R transmission, which added an overdrive gear to contribute to fuel economy and engine longevity.
For 1984, all Delta 88s were now Royale models. A new LS package denoted the top-end model.
The new front-wheel drive 98 debuted with a major redesign in 1985, and the new Delta 88 Royale Brougham LS model of the 88 took its place as Oldsmobile's most luxurious rear-wheel drive car.