All GM B-body full-size cars were completely restyled and enlarged for 1971, but continued to ride on a 124-inch (3,150 mm) wheelbase. It was available as a pillared four-door Town Sedan, two-door 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. All models received fuselage styling somewhat similar to what Chrysler Corporation introduced on its 1969 models, and new rooflines with a more squared off greenhouse for Town sedans and more rounded lines for Holiday sedans and coupes – the latter receiving reverting back to a semi-fastback format.Also new for 1971 was the Custom Cruiser station wagon, the first full-sized Olds wagon since 1964. It used the 88's B-body platform with a longer 127-inch (3,200 mm) wheelbase (matching the larger C-body Ninety-Eight) 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 full-size 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 91 RON octane, low-lead or unleaded gasoline. Vented 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 400 transmission were added to the standard equipment list.Other highlights for 1971 included a wrap-around instrument panel shared with Ninety-Eight and Toronado models (Toronados had a slightly smoother upper leading edge design) that was highlighted by a large square speedometer and all controls within easy reach of the driver, and a one-year only Flo-Through ventilation system that utilized vents in the trunklid. The system used on all GM B-, C- and E-body cars and the Chevrolet Vega, used the heater fan to draw air into the car from the cowl intake, and force it out through vents in the trunk lid or tailgate. In theory, passengers could enjoy fresh air even when the car was moving slowly or stopped, as in heavy traffic. In practice, however, it didn't work.Within weeks of the 1971 models' debut, however, Oldsmobile—and all other GM dealers—received multiple complaints from drivers who complained the ventilation system pulled cold air into the car before the heater could warm up—and could not be shut off. The ventilation system was extensively revised for 1972.For 1972, the Delta Custom series was dropped and the Royale series was expanded to include four-door Town and Holiday sedans. Advertised brake horsepower figures dropped to 155 for the base 350 two-barrel and 250 for the optional 455 four-barrel Rocket V8s thanks to an industry-wide switch in power measurements from the previous gross method (as measured by a dynamometer 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. Only minor trim changes were made this year that included revised "waterfall" grilles in front and four-segment taillights in the rear. Inside a revised "Flo-Through" ventilation system utilizing vents in the door jambs replaced the 1971 version which utilized vents in the trunklid.For 1973, wider and lower split waterfall grilles flanked a new federally-mandated 5 mph (8.0 km/h) front bumper on all Delta 88 models and larger one-piece rounded rectangular taillights 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 hp (160 kW) with single exhaust or 250 hp (186 kW) with dual exhausts. Model offerings were the same as 1972 with the Delta 88 Royale series now including the sole Olds convertible offering following the demise of the intermediate Cutlass Supreme convertible after 1972.In 1974, a 5 mph (8.0 km/h) rear bumper was added and taillights 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. The Delta 88 Royale ragtop was again the only convertible offered by Olds.Detail changes for 1975 included revised grilles and taillights 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 along with a one-year-only (and seldom-ordered) option of a Pontiac-built 400-cubic-inch V8 with two-barrel carburetor and 170 horsepower (130 kW) rating. All engines were 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, 1975. 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 red Delta 88 Royale rag top.For 1976, the final year of this generation, all Olds 88s received revised grille work, rectangular headlamps and parking lamps directly below instead of in the bumper, with Delta 88 Royale models also getting spring-loaded stand-up hood ornaments. 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. A one-year only option on Delta 88 Royale Holiday coupes was the Royale Crown Landau package that included a stainless steel roof bar, padded rear quarter vinyl roof, special hood ornament and color-keyed wheelcovers.